diff --git a/backend/locales/en.json b/backend/locales/en.json
index a3d1fdfcf..04818470f 100644
--- a/backend/locales/en.json
+++ b/backend/locales/en.json
@@ -1927,6 +1927,9 @@
   "editor.blockContent.drawioLoading": "Loading the draw.io editor...",
   "editor.blockContent.drawioTitle": "Draw.io editor",
   "editor.blockContent.drawioUnreachable": "The draw.io editor could not be loaded. Check that this address is reachable from your browser.",
+  "editor.blockContent.preview": "Preview",
+  "editor.blockContent.previewEmpty": "Nothing to preview yet — the preview is drawn from the source on the left.",
+  "editor.blockContent.source": "Source",
   "editor.blockContent.title": "Edit Block Content",
   "editor.blockContent.unknownEditor": "This block asks to be edited with something this wiki does not have.",
   "editor.blockNotEnabled": "This block is not enabled for this site, and will be removed when the page is saved. Blocks are managed in the administration area.",
@@ -2222,6 +2225,16 @@
   "editor.visual.block.remove": "Remove",
   "editor.visual.block.removeHint": "Remove this block",
   "editor.visual.block.removeKeepHint": "Remove this block, keeping what it holds",
+  "editor.visual.deflist.addDefinition": "Add definition",
+  "editor.visual.deflist.addDefinitionHint": "Add a definition below the row the cursor is in",
+  "editor.visual.deflist.addTerm": "Add term",
+  "editor.visual.deflist.addTermHint": "Add a term below the row the cursor is in",
+  "editor.visual.deflist.definition": "Definition",
+  "editor.visual.deflist.definitionPlaceholder": "What the term means",
+  "editor.visual.deflist.removeHint": "Remove this definition list and everything in it",
+  "editor.visual.deflist.term": "Term",
+  "editor.visual.deflist.termPlaceholder": "The word being defined",
+  "editor.visual.deflist.title": "Definition list",
   "editor.visual.image.alt": "Alternative Text",
   "editor.visual.image.altHint": "What stands in for the picture where it cannot be seen. Leave it empty where the image is decoration.",
   "editor.visual.image.edit": "Edit…",
@@ -2786,6 +2799,10 @@
   "userProfile.title": "User Profile",
   "welcome.admin": "Administration Area",
   "welcome.createHome": "Create the homepage",
+  "welcome.createHomeAsciidoc": "Using the AsciiDoc Editor",
+  "welcome.createHomeFailed": "Failed to open the editor.",
+  "welcome.createHomeMarkdown": "Using the Markdown Editor",
+  "welcome.createHomeVisual": "Using the Visual Editor",
   "welcome.homeDefault.content": "Write some content here...",
   "welcome.homeDefault.description": "Welcome to my wiki!",
   "welcome.homeDefault.title": "Home",
diff --git a/blocks/block-diagram/component.js b/blocks/block-diagram/component.js
index 18aced8e6..9a87b2ab3 100644
--- a/blocks/block-diagram/component.js
+++ b/blocks/block-diagram/component.js
@@ -64,6 +64,15 @@ flowchart LR
   B -->|Yes| C[Ship it]
   B -->|No| A
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the
+      Mermaid source on the left and this block, drawn from what is being typed, on the right. The
+      key is resolved to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'caption',
diff --git a/blocks/block-infobox/component.js b/blocks/block-infobox/component.js
index bd5cf2449..66642c13b 100644
--- a/blocks/block-infobox/component.js
+++ b/blocks/block-infobox/component.js
@@ -138,6 +138,15 @@ Public Transport:
   Monorail: false
 Website: https://montreal.ca
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the YAML
+      on the left and this block, drawn from what is being typed, on the right. The key is resolved
+      to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'name',
diff --git a/blocks/block-katex/component.js b/blocks/block-katex/component.js
index f625bc910..b8c92ecf4 100644
--- a/blocks/block-katex/component.js
+++ b/blocks/block-katex/component.js
@@ -55,6 +55,15 @@ export class BlockKatexElement extends LitElement {
     template: `\`\`\`latex
 x = \\frac{-b \\pm \\sqrt{b^2 - 4ac}}{2a}
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the TeX
+      on the left and this block, drawn from what is being typed, on the right. The key is resolved
+      to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'caption',
diff --git a/blocks/block-kroki/component.js b/blocks/block-kroki/component.js
index 5675222d1..a4279d6fc 100644
--- a/blocks/block-kroki/component.js
+++ b/blocks/block-kroki/component.js
@@ -96,6 +96,15 @@ digraph G {
   Hello -> World
 }
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the
+      diagram source on the left and this block, drawn from what is being typed, on the right. The
+      key is resolved to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'type',
diff --git a/blocks/block-mathjax/component.js b/blocks/block-mathjax/component.js
index a11d5f818..89fd2bf30 100644
--- a/blocks/block-mathjax/component.js
+++ b/blocks/block-mathjax/component.js
@@ -141,6 +141,15 @@ export class BlockMathjaxElement extends LitElement {
     template: `\`\`\`latex
 x = \\frac{-b \\pm \\sqrt{b^2 - 4ac}}{2a}
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the TeX
+      on the left and this block, drawn from what is being typed, on the right. The key is resolved
+      to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'caption',
diff --git a/blocks/block-plantuml/component.js b/blocks/block-plantuml/component.js
index c3ef2f125..cca99de35 100644
--- a/blocks/block-plantuml/component.js
+++ b/blocks/block-plantuml/component.js
@@ -69,6 +69,15 @@ Alice -> Bob : hello
 Bob --> Alice : hi
 @enduml
 \`\`\``,
+    /*
+      The body is a source an author types, so it is edited as one: `BlockContentCode` puts the
+      PlantUML source on the left and this block, drawn from what is being typed, on the right. The
+      key is resolved to a component by `BlockContentEditorOverlay`.
+
+      It is also the ONLY way to edit this block in the Visual editor: a block whose body is a
+      single fence is parsed as an atom there, so there is no caret to put inside it.
+    */
+    contentEditor: 'code',
     props: [
       {
         name: 'server',
diff --git a/frontend/src/components/BlockContentCode.vue b/frontend/src/components/BlockContentCode.vue
new file mode 100644
index 000000000..eec820bb4
--- /dev/null
+++ b/frontend/src/components/BlockContentCode.vue
@@ -0,0 +1,325 @@
+<template>
+  <div class="block-content-code">
+    <section class="block-content-code-pane">
+      <header class="block-content-code-bar">{{ t('editor.blockContent.source') }}</header>
+      <div ref="monacoEl" class="block-content-code-editor" />
+    </section>
+    <section class="block-content-code-pane block-content-code-pane--preview">
+      <header class="block-content-code-bar">{{ t('editor.blockContent.preview') }}</header>
+      <div class="block-content-code-preview page-contents">
+        <div v-if="state.empty" class="block-content-code-empty">
+          {{ t('editor.blockContent.previewEmpty') }}
+        </div>
+        <!--
+          Kept in the tree rather than torn out, so the element the block drew is not rebuilt from
+          nothing every time the source goes momentarily empty.
+        -->
+        <div v-show="!state.empty" ref="previewEl" />
+      </div>
+    </section>
+  </div>
+</template>
+
+<script setup>
+import { onBeforeUnmount, onMounted, reactive, ref, watch } from 'vue'
+import { useI18n } from 'vue-i18n'
+
+import * as monaco from 'monaco-editor'
+import { debounce } from 'es-toolkit/function'
+
+import { useCommonStore } from '@/stores/common'
+
+/**
+ * Source on the left, the block itself on the right — the body editor for every block whose content
+ * is code an author types.
+ *
+ * Which is most of them that have a body at all: a Mermaid diagram, a PlantUML or Kroki source, a TeX
+ * formula, an infobox's YAML. All of them store their body as one fenced source, all of them read it
+ * back out of a `<pre>` in their light DOM, and none of them could be edited in the Visual editor at
+ * all before this — a block holding a single fence is parsed as an ATOM there (`bodyIsContent` in
+ * `editor/visual/parse.js`), so there was no caret to put in it and nothing but the Parameters form
+ * to open over it.
+ *
+ * `BlockContentDrawio` is the other shape of body editor and the reason the registry exists: a
+ * drawing is edited on a canvas. This one is the shape everything else takes. See
+ * `BlockContentEditorOverlay` for the contract both implement.
+ *
+ * **The preview is the real block, not a rendering of one.** The same custom element the page draws,
+ * given the same attributes and the same `<pre>` the renderer would have left it — which is what the
+ * Visual editor's node view does for a block in the document, for the same reason: a second
+ * implementation of what a diagram looks like is a second thing to be wrong.
+ */
+
+// PROPS
+
+const props = defineProps({
+  /** The block's body: the source between the fences, without them. */
+  modelValue: {
+    type: String,
+    default: ''
+  },
+  /** The block's own parameters, which the preview is drawn with. */
+  params: {
+    type: Object,
+    default: () => ({})
+  },
+  /** The block as the API describes it. `block` is the half that matters — it names the element. */
+  block: {
+    type: Object,
+    default: () => ({})
+  },
+  /**
+   * The info string of the fence the source came out of (`mermaid`, `latex`, `yaml`, …), for the
+   * highlighting. Only the ones Monaco knows are used; see `monacoLanguage`.
+   */
+  lang: {
+    type: String,
+    default: ''
+  }
+})
+
+// EMITS
+
+const emit = defineEmits(['update:modelValue', 'save'])
+
+/** How long the author stops typing for before the block is drawn again. */
+const PREVIEW_DELAY = 600
+
+// STORES
+
+const commonStore = useCommonStore()
+
+// I18N
+
+const { t } = useI18n()
+
+// DATA
+
+const monacoEl = ref(null)
+const previewEl = ref(null)
+
+const state = reactive({
+  empty: !props.modelValue.trim()
+})
+
+let editor = null
+
+// METHODS
+
+/**
+ * The fence's language as a Monaco one, or plain text.
+ *
+ * Most of these languages are nobody's but their own tool's — Monaco has no Mermaid, no PlantUML, no
+ * Kroki and no TeX — so the list is asked rather than assumed. An id Monaco does not know is not an
+ * error there, it simply highlights nothing, but asking is what keeps `yaml` and `xml` working
+ * without a map of every name that happens to match.
+ */
+function monacoLanguage() {
+  const lang = props.lang.trim().toLowerCase()
+  const known = monaco.languages.getLanguages().some((entry) => entry.id === lang)
+  return known ? lang : 'plaintext'
+}
+
+/**
+ * The block, drawn from the source as it stands.
+ *
+ * A fresh element every time, because a block reads its body once — `firstUpdated`, in every one of
+ * them — so the only way to redraw one is to make another. Cheap for a diagram; for the two that talk
+ * to a server it is a request, which is what the debounce below is for.
+ */
+function renderPreview() {
+  const source = props.modelValue.trim()
+  state.empty = !source
+  if (!source || !previewEl.value) {
+    return
+  }
+  const name = props.block?.block ?? ''
+  if (!name) {
+    return
+  }
+  const tag = `block-${name}`
+  const element = document.createElement(tag)
+  /*
+    Only the parameters that are actually set, which is what the page itself carries: `blockValues`
+    fills in a blank for every prop the author left alone, and handing those to the element as empty
+    attributes is not the same as leaving them off.
+  */
+  for (const [key, value] of Object.entries(props.params ?? {})) {
+    if (value === undefined || value === null || value === '') {
+      continue
+    }
+    // -> A prop name a block declares is not necessarily a valid attribute name; a malformed one
+    //    should cost its own parameter and not the whole preview
+    try {
+      element.setAttribute(key, String(value))
+    } catch {
+      /* ignored */
+    }
+  }
+  /*
+    The `<pre>` is not decoration: every one of these blocks takes its source from
+    `querySelector('pre')` and falls back to its own text, and the fallback is the path that means
+    "this was not fenced" — `block-diagram` says so in its error message. So the preview hands it the
+    same shape the renderer does.
+  */
+  const pre = document.createElement('pre')
+  pre.textContent = source
+  element.append(pre)
+  previewEl.value.replaceChildren(element)
+
+  // -> Nothing draws until the element is upgraded, and a block is only fetched when a page uses it
+  if (!customElements.get(tag)) {
+    commonStore.loadBlocks([tag])
+  }
+}
+
+const renderPreviewSoon = debounce(renderPreview, PREVIEW_DELAY)
+
+// LIFECYCLE
+
+onMounted(() => {
+  // -> The markdown editor's theme, defined again here because that component may never have mounted
+  monaco.editor.defineTheme('wikijs', {
+    base: 'vs-dark',
+    inherit: true,
+    rules: [],
+    colors: {
+      'editor.background': '#070a0d',
+      'editor.lineHighlightBackground': '#0d1117',
+      'editorLineNumber.foreground': '#546e7a',
+      'editorGutter.background': '#0d1117'
+    }
+  })
+
+  editor = monaco.editor.create(monacoEl.value, {
+    automaticLayout: true,
+    fontSize: 14,
+    language: monacoLanguage(),
+    lineNumbersMinChars: 3,
+    minimap: { enabled: false },
+    padding: { top: 10, bottom: 10 },
+    scrollBeyondLastLine: false,
+    tabSize: 2,
+    theme: 'wikijs',
+    value: props.modelValue,
+    // -> Off: a diagram's source is structured by its indentation, and wrapping a long line of it
+    //    where the pane happens to end reads as a line of its own
+    wordWrap: 'off'
+  })
+
+  editor.onDidChangeModelContent(() => {
+    emit('update:modelValue', editor.getValue())
+    renderPreviewSoon()
+  })
+
+  /*
+    The same gesture as everywhere else in the app, and the overlay's Apply does the same thing. An
+    editor with a save of its own is what `@save` is for -- see the contract in the overlay.
+  */
+  editor.addCommand(monaco.KeyMod.CtrlCmd | monaco.KeyCode.KeyS, () => {
+    emit('save')
+  })
+
+  editor.focus()
+  renderPreview()
+})
+
+/*
+  The parameters can change under the preview: the Visual editor's own Parameters form is a different
+  overlay, but a block opened here twice in a session is not, and the preview has to be drawn with
+  what it is now rather than with what it was.
+*/
+watch(() => props.params, renderPreviewSoon, { deep: true })
+
+onBeforeUnmount(() => {
+  renderPreviewSoon.cancel()
+  /*
+    The editor first and its model second, as the two other Monaco sites in the app do. Monaco keeps
+    models in a registry of its own, so one left behind outlives the component that made it -- but
+    disposing it while the editor still holds it takes the editor's own teardown down with it
+    (`Model is disposed!`, out of an observer reading the version id as it unwinds).
+  */
+  const model = editor?.getModel()
+  editor?.dispose()
+  model?.dispose()
+  editor = null
+})
+</script>
+
+<style lang="scss">
+.block-content-code {
+  display: flex;
+  min-height: 0;
+  flex: 1 1 auto;
+
+  // -> Side by side is the point of this screen, but there is no room for two columns on a phone
+  @media (max-width: $breakpoint-sm-max) {
+    flex-direction: column;
+  }
+
+  &-pane {
+    display: flex;
+    flex-direction: column;
+    flex: 1 1 50%;
+    min-width: 0;
+    min-height: 0;
+
+    &--preview {
+      @at-root .body--light & {
+        background-color: #fff;
+        border-left: 1px solid $grey-4;
+      }
+      @at-root .body--dark & {
+        background-color: $dark-5;
+        border-left: 1px solid $dark-2;
+      }
+
+      @media (max-width: $breakpoint-sm-max) {
+        border-left: 0;
+      }
+    }
+  }
+
+  &-bar {
+    flex: 0 0 auto;
+    padding: 0.35rem 0.75rem;
+    font-size: 0.7rem;
+    font-weight: 500;
+    letter-spacing: 0.05em;
+    text-transform: uppercase;
+
+    @at-root .body--light & {
+      background-color: $grey-3;
+      color: $grey-7;
+      border-bottom: 1px solid $grey-4;
+    }
+    @at-root .body--dark & {
+      background-color: $dark-4;
+      color: $grey-5;
+      border-bottom: 1px solid $dark-2;
+    }
+  }
+
+  /*
+    Both halves are flex items of a column with a bar above them, so each needs `min-height: 0` of its
+    own: without it the box is sized by its content, and Monaco asking for the height of a box as tall
+    as itself resolves to nothing at all.
+  */
+  &-editor {
+    flex: 1 1 auto;
+    min-height: 0;
+  }
+
+  &-preview {
+    flex: 1 1 auto;
+    min-height: 0;
+    overflow: auto;
+    padding: 1rem;
+  }
+
+  &-empty {
+    font-style: italic;
+    opacity: 0.6;
+  }
+}
+</style>
diff --git a/frontend/src/components/BlockContentDrawio.vue b/frontend/src/components/BlockContentDrawio.vue
index e9b7e74c1..8dcdec422 100644
--- a/frontend/src/components/BlockContentDrawio.vue
+++ b/frontend/src/components/BlockContentDrawio.vue
@@ -65,6 +65,19 @@ const props = defineProps({
   params: {
     type: Object,
     default: () => ({})
+  },
+  /*
+    The other two halves of the editor contract, declared so they stay off this component's root
+    element rather than because a canvas has any use for them: a drawing is drawn, not highlighted,
+    and draw.io is the one editor that already knows what it is editing.
+  */
+  block: {
+    type: Object,
+    default: () => ({})
+  },
+  lang: {
+    type: String,
+    default: ''
   }
 })
 
diff --git a/frontend/src/components/BlockContentEditorOverlay.vue b/frontend/src/components/BlockContentEditorOverlay.vue
index 199691ab8..53bd7f0c6 100644
--- a/frontend/src/components/BlockContentEditorOverlay.vue
+++ b/frontend/src/components/BlockContentEditorOverlay.vue
@@ -40,6 +40,8 @@
           v-if="editorComponent"
           v-model="state.source"
           :params="params"
+          :block="block"
+          :lang="lang"
           @save="apply" />
         <div v-else class="p-6">
           <w-card class="bg-negative rounded text-white" flat>
@@ -81,6 +83,11 @@ import LoadingGeneric from './LoadingGeneric.vue'
  *   - a `modelValue` of the block's body as text, and `update:modelValue` when it changes;
  *   - a `params` object of the block's own parameters, for an editor that is configured by one — the
  *     server it talks to, say. Which of them mean anything is the editor's business alone;
+ *   - a `block` object, the block as the API describes it, for an editor that has to name the element
+ *     it is editing the body of — which is how the code editor draws its preview;
+ *   - a `lang` string, the info string of the fence the body came out of, for an editor that
+ *     highlights it. Both editors declare all four whether or not they read them, so the contract is
+ *     one shape rather than four combinations of it;
  *   - optionally `@save`, for an editor with a save gesture of its own, which applies and closes.
  *     An editor without one is applied by the button up here, which is always there either way.
  *
@@ -96,6 +103,10 @@ import LoadingGeneric from './LoadingGeneric.vue'
  * whole application, and it should not be in the bundle of a wiki that has never drawn one.
  */
 const EDITORS = {
+  code: defineAsyncComponent({
+    loader: () => import('./BlockContentCode.vue'),
+    loadingComponent: LoadingGeneric
+  }),
   drawio: defineAsyncComponent({
     loader: () => import('./BlockContentDrawio.vue'),
     loadingComponent: LoadingGeneric
@@ -120,6 +131,7 @@ const { t } = useI18n()
 const editorKey = siteStore.overlayOpts?.editor ?? ''
 const block = siteStore.overlayOpts?.block ?? {}
 const params = siteStore.overlayOpts?.params ?? {}
+const lang = siteStore.overlayOpts?.lang ?? ''
 const replace = siteStore.overlayOpts?.replace ?? null
 
 const state = reactive({
@@ -132,10 +144,15 @@ const editorComponent = computed(() => EDITORS[editorKey] ?? null)
 
 // METHODS
 
+/*
+  Always emitted, `replace` or no `replace`. It is the MARKDOWN editor that needs one -- a line range
+  to write the body back over -- and the Visual editor deliberately sends none, because a block there
+  is a node and it kept the position of the one it opened. Guarding the emit on it therefore meant
+  Apply did nothing at all on that side: the only block with a body editor was draw.io, where the
+  drawing came back and was then dropped on the floor.
+*/
 function apply() {
-  if (replace) {
-    EVENT_BUS.emit('replaceBlockContent', { source: state.source, replace })
-  }
+  EVENT_BUS.emit('replaceBlockContent', { source: state.source, replace })
   close()
 }
 
diff --git a/frontend/src/components/EditorMarkdown.vue b/frontend/src/components/EditorMarkdown.vue
index 94bb500a0..317cda26c 100644
--- a/frontend/src/components/EditorMarkdown.vue
+++ b/frontend/src/components/EditorMarkdown.vue
@@ -780,6 +780,7 @@ function editBlockContent(line, name) {
       block: definition,
       params: blockValues(found, definition),
       source: content.source,
+      lang: content.language,
       // -> Where it goes back, and in what: the editor is handed text and hands text back, and the
       //    fence it lives in is this side's business
       replace: content
@@ -794,6 +795,11 @@ function editBlockContent(line, name) {
  * edit and one undo, and the opening line of the block is not touched at all.
  */
 function replaceBlockContentClb({ source, replace }) {
+  // -> The Visual editor's own answer carries no range; only one editor is ever mounted, so this is
+  //    belt and braces rather than a case that happens
+  if (!replace) {
+    return
+  }
   const model = editor.getModel()
   editor.executeEdits('blockContent', [
     {
diff --git a/frontend/src/components/EditorVisual.vue b/frontend/src/components/EditorVisual.vue
index 09b6f3544..1069c1ef0 100644
--- a/frontend/src/components/EditorVisual.vue
+++ b/frontend/src/components/EditorVisual.vue
@@ -394,6 +394,7 @@ import 'prosemirror-gapcursor/style/gapcursor.css'
 import { createVisualEditor } from '@/editor/visual'
 import { readFencedBody, writeFencedBody } from '@/editor/visual/blockBody'
 import {
+  insertDefinitionList as insertDefinitionListCommand,
   insertNode,
   insertTable as insertTableCommand,
   markActive,
@@ -889,12 +890,11 @@ function insertIcon(reference) {
  * A definition list with one empty pair, ready to be typed into.
  *
  * The same shape the Markdown editor's own button produces, which is a term and a definition rather
- * than a bare `dl` — an empty list is not something markdown can even express.
+ * than a bare `dl` — an empty list is not something markdown can even express. Where it goes and
+ * where the caret lands afterwards are the command's business; see it for why that matters.
  */
 function insertDefinitionList() {
-  const term = schema.nodes.definition_term.createAndFill()
-  const description = schema.nodes.definition_description.createAndFill()
-  run(insertNode(schema.nodes.definition_list, null, [term, description]))
+  run(insertDefinitionListCommand())
 }
 
 /** The next free footnote label, counting the ones the document already carries. */
@@ -1045,6 +1045,7 @@ function editBlockContent(node, pos) {
       block: definition,
       params: { ...node.attrs.blockAttrs },
       source: body.source,
+      lang: body.lang,
       // -> The Markdown editor puts a line range here; nothing on this side needs one, since the
       //    block is a node and `editingBlockPos` is where it is
       replace: null
@@ -1052,19 +1053,26 @@ function editBlockContent(node, pos) {
   })
 }
 
-/** A block body an editor produced, back onto the node it came from. */
+/**
+ * A block body an editor produced, back onto the node it came from.
+ *
+ * The position is taken into a local BEFORE the field is cleared, and the field is cleared whichever
+ * way this returns: writing it back through `editingBlockPos` wrote it back through `null`, which is
+ * position -1 to ProseMirror and an exception rather than an edit.
+ */
 function replaceBlockContentClb({ source }) {
-  if (editingBlockPos === null || !editor) {
+  const pos = editingBlockPos
+  editingBlockPos = null
+  if (pos === null || !editor) {
     return
   }
   const view = editor.view
-  const node = view.state.doc.nodeAt(editingBlockPos)
-  editingBlockPos = null
+  const node = view.state.doc.nodeAt(pos)
   if (!node || node.type !== schema.nodes.block_component) {
     return
   }
   view.dispatch(
-    view.state.tr.setNodeMarkup(editingBlockPos, undefined, {
+    view.state.tr.setNodeMarkup(pos, undefined, {
       ...node.attrs,
       body: writeFencedBody(node.attrs.body, source)
     })
diff --git a/frontend/src/components/WelcomeOverlay.vue b/frontend/src/components/WelcomeOverlay.vue
index f3682a5f9..c2daa1ece 100644
--- a/frontend/src/components/WelcomeOverlay.vue
+++ b/frontend/src/components/WelcomeOverlay.vue
@@ -11,7 +11,7 @@
             <w-list padding>
               <w-item clickable @click="createHomePage(`visual`)" v-if="siteStore.editors.visual">
                 <blueprint-icon icon="google-presentation" />
-                <w-item-section class="pr-2">Using the Visual Editor</w-item-section>
+                <w-item-section class="pr-2">{{ t(`welcome.createHomeVisual`) }}</w-item-section>
                 <w-item-section side><w-icon name="mdi:chevron-right" /></w-item-section>
               </w-item>
               <w-item
@@ -19,7 +19,7 @@
                 @click="createHomePage(`markdown`)"
                 v-if="siteStore.editors.markdown">
                 <blueprint-icon icon="markdown" />
-                <w-item-section class="pr-2">Using the Markdown Editor</w-item-section>
+                <w-item-section class="pr-2">{{ t(`welcome.createHomeMarkdown`) }}</w-item-section>
                 <w-item-section side><w-icon name="mdi:chevron-right" /></w-item-section>
               </w-item>
               <w-item
@@ -27,7 +27,7 @@
                 @click="createHomePage(`asciidoc`)"
                 v-if="flagsStore.experimental && siteStore.editors.asciidoc">
                 <blueprint-icon icon="asciidoc" />
-                <w-item-section class="pr-2">Using the AsciiDoc Editor</w-item-section>
+                <w-item-section class="pr-2">{{ t(`welcome.createHomeAsciidoc`) }}</w-item-section>
                 <w-item-section side><w-icon name="mdi:chevron-right" /></w-item-section>
               </w-item>
             </w-list>
@@ -107,7 +107,7 @@ async function createHomePage(editor) {
     siteStore.overlay = 'Welcome'
     notify({
       type: 'negative',
-      message: 'Failed to open the editor.',
+      message: t('welcome.createHomeFailed'),
       caption: err.message
     })
   }
@@ -124,9 +124,22 @@ function loadAdmin() {
 .welcome {
   background: #fff radial-gradient(ellipse, #fff, #ddd);
   color: $grey-9;
-  height: 100vh;
+  // -> The panel this is slotted into is what owns the shape: WDialog rounds it and clips to that
+  //    radius, and hands the radius down to its child with `border-radius: inherit`. A radius of its
+  //    own here was the larger of the two, so the panel's own top corners -- the dark first 10px of
+  //    the gradient `.main-overlay` paints on it -- showed in the gap between the two curves.
+  height: 100%;
   border: 1px solid #eee;
-  border-radius: 25px !important;
+
+  // -> This sheet paints over the dialog surface underneath it, so it carries its own colours in
+  //    both themes rather than letting `.main-overlay`'s show through -- which is why it was white
+  //    on a dark wiki, with the menu it opens correctly dark and the two disagreeing. Dark mirrors
+  //    light a step at a time: the sheet, the vignette at its edges, the rule round it, the text.
+  @at-root .body--dark & {
+    background: $dark-5 radial-gradient(ellipse, $dark-4, $dark-6);
+    color: $grey-4;
+    border-color: $dark-2;
+  }
 
   &-bg {
     position: absolute;
@@ -138,6 +151,13 @@ function loadAdmin() {
     border-radius: 50%;
     filter: blur(100px);
     transform: translate(-50%, -55%);
+
+    // -> The lower half of the blob is the sheet's own colour, so what shows is the glow above it
+    //    and not a pale smear across the middle. $blue-8 rather than the lighter $blue-5: the same
+    //    glow needs less lightness to read against near-black than it does against white.
+    @at-root .body--dark & {
+      background: linear-gradient(0, $dark-5 50%, $blue-8 50%);
+    }
   }
 
   &-content {
@@ -179,6 +199,10 @@ function loadAdmin() {
     color: $blue-7;
     line-height: 1.2rem;
     margin-top: 1rem;
+
+    @at-root .body--dark & {
+      color: $blue-4;
+    }
   }
 
   &-actions {
diff --git a/frontend/src/css/_visual-editor.scss b/frontend/src/css/_visual-editor.scss
index 43990a448..7eb35428d 100644
--- a/frontend/src/css/_visual-editor.scss
+++ b/frontend/src/css/_visual-editor.scss
@@ -712,6 +712,80 @@
   }
 }
 
+/*
+  A definition list.
+
+  The page draws a `dl` as a term in bold with its definition indented under it, which is all the
+  distinction a READER needs and none of what an author does: both rows are empty when the list is
+  made, and an empty `dt` and an empty `dd` are the same nothing. So the editor adds a gutter that
+  names each row, and shows in the row itself what belongs there while it is empty.
+
+  Everything here is scoped to `.visual-deflist`, the wrapper the node view puts round the list, so
+  the page's own definition lists are untouched -- and the geometry inside is still `_page-contents`'.
+*/
+.visual-deflist {
+  border: 1px solid $grey-4;
+  border-radius: 4px;
+  margin: 0 0 1.15em;
+  overflow: hidden;
+
+  .body--dark & {
+    border-color: $grey-8;
+  }
+}
+
+.visual-deflist-rows {
+  /* -> The left padding is the gutter the labels sit in; the rows themselves start after it */
+  margin: 0;
+  padding: 0.6rem 0.75rem 0.7rem 7rem;
+}
+
+.visual-deflist dt,
+.visual-deflist dd {
+  position: relative;
+
+  /*
+    The row's name, in the gutter. Against the row rather than against the list, so a definition's
+    label follows the indent of the definition it names -- the two read as a pair that way.
+  */
+  &::before {
+    content: attr(data-label);
+    position: absolute;
+    right: calc(100% + 0.6rem);
+    top: 0.15em;
+    font-size: 0.6rem;
+    font-weight: 600;
+    letter-spacing: 0.5px;
+    text-transform: uppercase;
+    white-space: nowrap;
+    color: $grey-6;
+    user-select: none;
+
+    .body--dark & {
+      color: $grey-6;
+    }
+  }
+
+  /*
+    What goes in a row nobody has typed in yet. `pointer-events: none` so that clicking the words
+    still puts the caret in the row they are standing in for, rather than at the end of the line.
+  */
+  &.is-empty::after {
+    content: attr(data-placeholder);
+    position: absolute;
+    top: 0;
+    left: 0;
+    font-weight: 400;
+    font-style: italic;
+    color: $grey-5;
+    pointer-events: none;
+
+    .body--dark & {
+      color: $grey-7;
+    }
+  }
+}
+
 /* A footnote's body, labelled with the reference that points at it. */
 .visual-footnote {
   display: flex;
diff --git a/frontend/src/editor/visual/commands.js b/frontend/src/editor/visual/commands.js
index 6e8637116..6825237ed 100644
--- a/frontend/src/editor/visual/commands.js
+++ b/frontend/src/editor/visual/commands.js
@@ -236,6 +236,57 @@ export function insertNode(type, attrs = {}, content = null) {
   }
 }
 
+/**
+ * An empty definition list — one term and its definition — with the caret in the term.
+ *
+ * Built as nodes rather than parsed from markdown, unlike most of what the toolbar inserts: an empty
+ * definition list is not something markdown can express, since `: ` on a line with nothing above it
+ * is a paragraph that starts with a colon.
+ *
+ * `insertNode` is deliberately not used, and that is the reason this exists. It inserts through
+ * `replaceSelectionWith`, which for this node leaves the caret in the paragraph the button was
+ * pressed in — so the first word an author typed went above the list instead of into it, which is
+ * most of what made the list feel broken. Here the position is worked out first and the caret put
+ * where the typing is meant to start.
+ */
+export function insertDefinitionList() {
+  return (state, dispatch) => {
+    const list = schema.nodes.definition_list.createAndFill(null, [
+      schema.nodes.definition_term.createAndFill(),
+      schema.nodes.definition_description.createAndFill()
+    ])
+    if (!list) {
+      return false
+    }
+    if (dispatch) {
+      const { $from } = state.selection
+      /*
+        Where a block construct goes, by the same rule `insertMarkdown` follows: in place of the
+        textblock the caret is in when that block is empty -- inserting a list into the empty
+        paragraph at the end of a page should not strand that paragraph above it -- and after that
+        block otherwise. A selection with no textblock around it at all (a node selected whole) puts
+        the list at its own position.
+      */
+      const replacing =
+        $from.depth > 0 && $from.parent.isTextblock && $from.parent.content.size === 0
+      let at = $from.pos
+      if ($from.depth > 0) {
+        at = replacing ? $from.before() : $from.after()
+      }
+      const tr = state.tr
+      if (replacing) {
+        tr.replaceWith(at, $from.after(), list)
+      } else {
+        tr.insert(at, list)
+      }
+      // -> Two positions in: past the list's own opening token, then past the term's
+      tr.setSelection(TextSelection.near(tr.doc.resolve(at + 2)))
+      dispatch(tr.scrollIntoView())
+    }
+    return true
+  }
+}
+
 /** A table of `rows` × `cols`, its first row a header. */
 export function insertTable(rows = 3, cols = 3) {
   return (state, dispatch) => {
@@ -252,6 +303,94 @@ export function insertTable(rows = 3, cols = 3) {
   }
 }
 
+/**
+ * Whether a row of a definition list has never been typed into.
+ *
+ * A different question of each kind: a term holds inline content, while a definition holds blocks, so
+ * an untouched definition is a paragraph with nothing in it rather than nothing at all.
+ */
+function rowIsEmpty(row) {
+  return row.type === schema.nodes.definition_term
+    ? row.content.size === 0
+    : row.childCount === 1 && row.firstChild.content.size === 0
+}
+
+/**
+ * Enter inside a definition list: term, definition, term, definition — and out at the end.
+ *
+ * The gesture that makes a definition list writable at all. A `dl` is two alternating node types with
+ * no visible difference between them until they hold text, so the default `splitBlock` — which makes
+ * another node of the SAME type — left an author typing a second term where they meant to type its
+ * definition, with no indication that anything was wrong.
+ *
+ * So Enter alternates:
+ *
+ *   - in a term, the definition below it — the caret into the empty one already there, which is the
+ *     shape the toolbar's own button produces, or a new one where there is none;
+ *   - in a definition, the next term, on the same rule;
+ *   - in an EMPTY row that is the last in the list, out of the list entirely, as pressing Enter twice
+ *     leaves any other list.
+ *
+ * An empty row in the MIDDLE is left to the first two rules rather than splitting the list in half:
+ * markdown has no way to write two definition lists in a row without something between them anyway.
+ *
+ * A definition that runs to more than one paragraph is not reachable this way, which is deliberate:
+ * a definition list is one line per definition almost everywhere it is used, and Shift-Enter still
+ * puts a line break in a long one.
+ */
+export function splitDefinitionItem(state, dispatch) {
+  const { $from, empty } = state.selection
+  if (!empty) {
+    return false
+  }
+
+  let depth = $from.depth
+  while (
+    depth > 0 &&
+    $from.node(depth).type !== schema.nodes.definition_term &&
+    $from.node(depth).type !== schema.nodes.definition_description
+  ) {
+    depth -= 1
+  }
+  if (depth === 0 || $from.node(depth - 1).type !== schema.nodes.definition_list) {
+    return false
+  }
+
+  const row = $from.node(depth)
+  const list = $from.node(depth - 1)
+  const index = $from.index(depth - 1)
+  const isLast = index === list.childCount - 1
+  const wanted =
+    row.type === schema.nodes.definition_term
+      ? schema.nodes.definition_description
+      : schema.nodes.definition_term
+  const next = isLast ? null : list.child(index + 1)
+
+  if (!dispatch) {
+    return true
+  }
+
+  const tr = state.tr
+  const at = $from.after(depth)
+  if (next && next.type === wanted && rowIsEmpty(next)) {
+    // -> Into the row that is already there, rather than another empty one beside it
+    tr.setSelection(TextSelection.near(tr.doc.resolve(at + 1)))
+  } else if (isLast && rowIsEmpty(row)) {
+    /*
+      Out of the list. The whole list goes when the empty row was all of it -- a `dl` with no rows is
+      not a document the schema allows, and it is not something markdown can write either.
+    */
+    const from = list.childCount === 1 ? $from.before(depth - 1) : $from.before(depth)
+    tr.replaceWith(from, $from.after(depth - 1), schema.nodes.paragraph.createAndFill())
+    tr.setSelection(TextSelection.near(tr.doc.resolve(from + 1)))
+  } else {
+    tr.insert(at, wanted.createAndFill())
+    tr.setSelection(TextSelection.near(tr.doc.resolve(at + 1)))
+  }
+  dispatch(tr.scrollIntoView())
+  return true
+}
+
 /** Whether a mark is on the selection, or would be on what is typed next. */
 export function markActive(state, type) {
   const { from, $from, to, empty } = state.selection
@@ -309,7 +448,12 @@ export function buildKeymap({ collab = false } = {}) {
     'Mod-Shift-.': wrapIn(schema.nodes.blockquote),
     'Mod-Shift-Enter': toggleTaskChecked,
 
-    Enter: chainCommands(splitListItem(schema.nodes.list_item), baseKeymap.Enter),
+    // -> Definition lists first: their rows alternate, which neither of the other two knows about
+    Enter: chainCommands(
+      splitDefinitionItem,
+      splitListItem(schema.nodes.list_item),
+      baseKeymap.Enter
+    ),
     Tab: chainCommands(goToNextCell(1), sinkListItem(schema.nodes.list_item)),
     'Shift-Tab': chainCommands(goToNextCell(-1), liftListItem(schema.nodes.list_item)),
 
diff --git a/frontend/src/editor/visual/nodeviews.js b/frontend/src/editor/visual/nodeviews.js
index ee6d0fa50..545e90b75 100644
--- a/frontend/src/editor/visual/nodeviews.js
+++ b/frontend/src/editor/visual/nodeviews.js
@@ -883,6 +883,143 @@ class AbbreviationView {
   }
 }
 
+/**
+ * A definition list, with a bar of its own and every row saying which half of the pair it is.
+ *
+ * The one construct in this editor with nothing to look at. A `dl` is terms and definitions
+ * alternating, both of them empty when the list is made, and the page styles alone say nothing: an
+ * author who pressed the toolbar button got a blank patch, could not tell which of the two invisible
+ * rows the caret was in, and had no way to add a third. So the rows are labelled in a gutter (see
+ * `DefinitionRowView`), an empty one shows what belongs in it, and the bar offers the two things
+ * there are to do to a list that already exists.
+ *
+ * The bar is chrome, so the `dl` the rows live in is a child of it rather than the node's own DOM.
+ */
+class DefinitionListView {
+  constructor(node, view, getPos, context) {
+    this.node = node
+    this.view = view
+    this.getPos = getPos
+    this.context = context
+
+    this.dom = document.createElement('div')
+    this.dom.className = 'visual-deflist'
+
+    this.header = blockHeader({
+      name: context.t('editor.visual.deflist.title'),
+      attrs: null,
+      actions: [
+        {
+          label: context.t('editor.visual.deflist.addTerm'),
+          title: context.t('editor.visual.deflist.addTermHint'),
+          run: () => this.addRow(schema.nodes.definition_term)
+        },
+        {
+          label: context.t('editor.visual.deflist.addDefinition'),
+          title: context.t('editor.visual.deflist.addDefinitionHint'),
+          run: () => this.addRow(schema.nodes.definition_description)
+        },
+        {
+          label: context.t('editor.visual.block.remove'),
+          title: context.t('editor.visual.deflist.removeHint'),
+          run: () => this.context.removeNode(this.getPos())
+        }
+      ]
+    })
+
+    this.contentDOM = document.createElement('dl')
+    this.contentDOM.className = 'visual-deflist-rows'
+    this.dom.append(this.header, this.contentDOM)
+  }
+
+  /**
+   * A new row, and the caret in it.
+   *
+   * After the row the author is in rather than at the end of the list: a list long enough to need
+   * another term in the middle of it is exactly the list where being sent to the bottom is wrong. The
+   * end is the fallback, for a press with the selection somewhere else entirely.
+   */
+  addRow(type) {
+    const pos = this.getPos()
+    if (pos === undefined) {
+      return
+    }
+    const row = type.createAndFill()
+    if (!row) {
+      return
+    }
+    let at = pos + this.node.nodeSize - 1
+    const { from } = this.view.state.selection
+    this.node.forEach((child, offset) => {
+      const start = pos + 1 + offset
+      if (from >= start && from <= start + child.nodeSize) {
+        at = start + child.nodeSize
+      }
+    })
+    const tr = this.view.state.tr.insert(at, row)
+    tr.setSelection(TextSelection.near(tr.doc.resolve(at + 1)))
+    this.view.dispatch(tr.scrollIntoView())
+    this.view.focus()
+  }
+
+  update(node) {
+    if (node.type !== this.node.type) {
+      return false
+    }
+    this.node = node
+    return true
+  }
+
+  ignoreMutation(mutation) {
+    return this.header.contains(mutation.target)
+  }
+
+  stopEvent(event) {
+    return this.header.contains(event.target)
+  }
+}
+
+/**
+ * One row of a definition list — the `dt` or the `dd` itself, told what it is.
+ *
+ * The element is its own content: there is nowhere to put a label INSIDE a node whose children are
+ * the document's own text without ProseMirror reading it as something an author typed. So the label
+ * and the placeholder are data attributes that `_visual-editor.scss` draws as pseudo-elements, and
+ * the only thing this view does is keep them, and the empty flag, in step with the node.
+ */
+class DefinitionRowView {
+  constructor(node, { tag, label, placeholder, isEmpty }) {
+    this.node = node
+    this.isEmpty = isEmpty
+
+    this.dom = document.createElement(tag)
+    // -> Its own content: the row is a textblock, and a wrapper would put a node between the `dl` and
+    //    the rows that the page's own stylesheet does not have
+    this.contentDOM = this.dom
+    this.dom.dataset.label = label
+    this.dom.dataset.placeholder = placeholder
+    this.apply(node)
+  }
+
+  apply(node) {
+    this.dom.classList.toggle('is-empty', this.isEmpty(node))
+  }
+
+  update(node) {
+    if (node.type !== this.node.type) {
+      return false
+    }
+    this.node = node
+    this.apply(node)
+    return true
+  }
+
+  /** The class and the two data attributes are this view's own; the text inside them is not. */
+  ignoreMutation(mutation) {
+    return mutation.type === 'attributes'
+  }
+}
+
 /** A footnote's body, labelled with the reference that points at it. */
 class FootnoteDefinitionView {
   constructor(node) {
@@ -1031,6 +1168,22 @@ export function createNodeViews(context) {
     },
     code_block: (node, view, getPos) => new CodeBlockView(node, view, getPos, context),
     alert: (node, view, getPos) => new AlertView(node, view, getPos, context),
+    definition_list: (node, view, getPos) => new DefinitionListView(node, view, getPos, context),
+    definition_term: (node) =>
+      new DefinitionRowView(node, {
+        tag: 'dt',
+        label: context.t('editor.visual.deflist.term'),
+        placeholder: context.t('editor.visual.deflist.termPlaceholder'),
+        isEmpty: (row) => row.content.size === 0
+      }),
+    definition_description: (node) =>
+      new DefinitionRowView(node, {
+        tag: 'dd',
+        label: context.t('editor.visual.deflist.definition'),
+        placeholder: context.t('editor.visual.deflist.definitionPlaceholder'),
+        // -> A definition holds blocks, so an untouched one is a paragraph with nothing in it
+        isEmpty: (row) => row.childCount === 1 && row.firstChild.content.size === 0
+      }),
     abbreviation: (node, view, getPos) => new AbbreviationView(node, view, getPos, context),
     footnote_definition: (node) => new FootnoteDefinitionView(node),
     raw_block: (node, view, getPos) => new RawBlockView(node, view, getPos, context),