Added hint

app/src/main/res/layout/fragment_options_display.xml

@@ -74,6 +74,18 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/tvStartup" />
 
+        <eu.faircode.email.FixedTextView
+            android:id="@+id/tvStartupHint"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginEnd="48dp"
+            android:text="@string/title_advanced_startup_hint"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/spStartup" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swCards"
             android:layout_width="0dp"
@@ -83,7 +95,7 @@
             android:text="@string/title_advanced_cards"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/spStartup"
+            app:layout_constraintTop_toBottomOf="@id/tvStartupHint"
             app:switchPadding="12dp" />
 
         <androidx.appcompat.widget.SwitchCompat

app/src/main/res/values/strings.xml

@@ -465,6 +465,7 @@
     <string name="title_advanced_browse_hint">Fetch more messages when scrolling down</string>
 
     <string name="title_advanced_layout_hint">Switching to a more compact layout and changing the message text size can be done in the top action bar menu in the message view</string>
+    <string name="title_advanced_startup_hint">Long press any folder in the folder list to add or remove it from the list of unified folders</string>
     <string name="title_advanced_date_hint">Messages are only grouped by date if they are sorted by time</string>
     <string name="title_advanced_navbar_colorize_hint">Whether this works depends on the Android version and variant</string>
     <string name="title_advanced_threading_hint">Group messages related to each other</string>