diff --git a/Components/ScintEdit.pas b/Components/ScintEdit.pas
index 5b5246455..f05769399 100644
--- a/Components/ScintEdit.pas
+++ b/Components/ScintEdit.pas
@@ -65,6 +65,7 @@   TScintRangeList = class(TList<TScintRange>)
   TScintRectangle = record
     Left, Top, Right, Bottom: Integer;
   end;
+  TScintSelectionMode = (ssmStream, ssmRectangular, ssmLines, ssmThinRectangular);
   TScintStyleNumber = 0..StyleNumbers-1;
   TScintVirtualSpaceOption = (svsRectangularSelection, svsUserAccessible,
     svsNoWrapLineStart);
@@ -79,6 +80,8 @@   TScintRangeToFormat = record
   TScintEditStrings = class;
   TScintCustomStyler = class;
 
+  EScintEditError = class(Exception);
+
   TScintEdit = class(TWinControl)
   private
     FAcceptDroppedFiles: Boolean;
@@ -135,6 +138,7 @@   TScintEdit = class(TWinControl)
     function GetSelectionAnchorPosition(Selection: Integer): Integer;
     function GetSelectionCaretPosition(Selection: Integer): Integer;
     function GetSelectionCount: Integer;
+    function GetSelectionMode: TScintSelectionMode;
     function GetSelText: String;
     function GetTopLine: Integer;
     function GetZoom: Integer;
@@ -157,6 +161,7 @@   TScintEdit = class(TWinControl)
     procedure SetSelection(const Value: TScintRange);
     procedure SetSelectionAnchorPosition(Selection: Integer; const AnchorPos: Integer);
     procedure SetSelectionCaretPosition(Selection: Integer; const CaretPos: Integer);
+    procedure SetSelectionMode(const Value: TScintSelectionMode);
     procedure SetSelText(const Value: String);
     procedure SetStyler(const Value: TScintCustomStyler);
     procedure SetTabWidth(const Value: Integer);
@@ -185,7 +190,8 @@   TScintEdit = class(TWinControl)
     procedure CheckPosRange(const StartPos, EndPos: Integer);
     procedure CreateParams(var Params: TCreateParams); override;
     procedure CreateWnd; override;
-    class procedure Error(const S: String);
+    class function GetErrorException(const S: String): EScintEditError;
+    class procedure Error(const S: String); overload;
     class procedure ErrorFmt(const S: String; const Args: array of const);
     function GetMainSelection: Integer;
     function GetTarget: TScintRange;
@@ -316,6 +322,7 @@   TScintEdit = class(TWinControl)
     property SelectionAnchorPosition[Selection: Integer]: Integer read GetSelectionAnchorPosition write SetSelectionAnchorPosition;
     property SelectionCaretPosition[Selection: Integer]: Integer read GetSelectionCaretPosition write SetSelectionCaretPosition;
     property SelectionCount: Integer read GetSelectionCount;
+    property SelectionMode: TScintSelectionMode read GetSelectionMode write SetSelectionMode;
     property SelText: String read GetSelText write SetSelText;
     property Styler: TScintCustomStyler read FStyler write SetStyler;
     property TopLine: Integer read GetTopLine write SetTopLine;
@@ -462,8 +469,6 @@   TScintPixmap = class
     property Pixmap: Pointer read GetPixmap;
   end;
 
-  EScintEditError = class(Exception);
-
 function ScintRawStringIsBlank(const S: TScintRawString): Boolean;
 
 implementation
@@ -743,9 +748,14 @@ procedure TScintEdit.EndUndoAction;
   Call(SCI_ENDUNDOACTION, 0, 0);
 end;
 
+class function TScintEdit.GetErrorException(const S: String): EScintEditError;
+begin
+  Result := EScintEditError.Create('TScintEdit error: ' + S);
+end;
+
 class procedure TScintEdit.Error(const S: String);
 begin
-  raise EScintEditError.Create('TScintEdit error: ' + S);
+  raise GetErrorException(S);
 end;
 
 class procedure TScintEdit.ErrorFmt(const S: String; const Args: array of const);
@@ -856,8 +866,9 @@ function TScintEdit.GetLineEndings: TScintLineEndings;
   case Call(SCI_GETEOLMODE, 0, 0) of
     SC_EOL_CR: Result := sleCR;
     SC_EOL_LF: Result := sleLF;
+    SC_EOL_CRLF: Result := sleCRLF;
   else
-    Result := sleCRLF;
+    raise GetErrorException('Unexpected SCI_GETEOLMODE result');
   end;
 end;
 
@@ -1077,6 +1088,18 @@ function TScintEdit.GetSelectionCount: Integer;
   Result := Call(SCI_GETSELECTIONS, 0, 0);
 end;
 
+function TScintEdit.GetSelectionMode: TScintSelectionMode;
+begin
+  case Call(SCI_GETSELECTIONMODE, 0, 0) of
+    SC_SEL_STREAM: Result := ssmStream;
+    SC_SEL_RECTANGLE: Result := ssmRectangular;
+    SC_SEL_LINES: Result := ssmLines;
+    SC_SEL_THIN: Result := ssmThinRectangular;
+  else
+    raise GetErrorException('Unexpected SCI_GETSELECTIONMODE result');
+  end;
+end;
+
 function TScintEdit.GetSelText: String;
 begin
   Result := ConvertRawStringToString(GetRawSelText);
@@ -1536,6 +1559,21 @@ procedure TScintEdit.SetSelectionCaretPosition(Selection: Integer;
   Call(SCI_SETSELECTIONNCARET, Selection, CaretPos);
 end;
 
+procedure TScintEdit.SetSelectionMode(const Value: TScintSelectionMode);
+begin
+  var Mode: Integer;
+  if Value = ssmStream then
+    Mode := SC_SEL_STREAM
+  else if Value = ssmRectangular then
+    Mode := SC_SEL_RECTANGLE
+  else if Value = ssmLines then
+    Mode := SC_SEL_LINES
+  else
+    Mode := SC_SEL_THIN;
+  { Note this uses *CHANGE* and not *SET* }
+  Call(SCI_CHANGESELECTIONMODE, Mode, 0);
+end;
+
 procedure TScintEdit.SetSelText(const Value: String);
 begin
   SetRawSelText(ConvertStringToRawString(Value));
diff --git a/Projects/Src/CompForm.pas b/Projects/Src/CompForm.pas
index e3e147243..95d444f9c 100644
--- a/Projects/Src/CompForm.pas
+++ b/Projects/Src/CompForm.pas
@@ -2807,6 +2807,18 @@ procedure TCompileForm.HDocClick(Sender: TObject);
 procedure TCompileForm.MemoKeyDown(Sender: TObject; var Key: Word;
   Shift: TShiftState);
 begin
+  if Key in [VK_LEFT, VK_RIGHT, VK_UP, VK_DOWN, VK_HOME, VK_END] then begin
+    var Memo := Sender as TScintEdit;
+    if Memo.SelectionMode in [ssmRectangular, ssmThinRectangular] then begin
+       { Allow left/right/etc. navigation with rectangular selection, see
+         https://sourceforge.net/p/scintilla/feature-requests/1275/ and
+         https://sourceforge.net/p/scintilla/bugs/2412/#cb37
+         Notepad++ calls this "Enable Column Selection to Multi-editing" which
+         is on by default and in VSCode and VS it's also on by default. }
+      Memo.SelectionMode := ssmStream;
+    end;
+  end;
+
   if Key = VK_F1 then begin
     var HelpFile := GetHelpFile;
     if Assigned(HtmlHelp) then begin
diff --git a/whatsnew.htm b/whatsnew.htm
index 5f68b86a8..b144fb064 100644
--- a/whatsnew.htm
+++ b/whatsnew.htm
@@ -38,9 +38,9 @@
   <li>Added shortcut to add the next occurrence of the current word or selected text as an additional selection (Alt+Shift+.).</li>
   <li>Added shortcut to select all occurrences of the current word or selected text (Alt+Shift+;).</li>
   <li>Added shortcuts to add a word or line as an additional selection (Ctrl+Double Click and Ctrl+Triple Click).</li>
-  <li>Multiple selection now works over horizontal movement and selection commands.</li>
-  <li>Multiple selection now works over line up and down movement and selection commands.</li>
+  <li>Multiple selection now works over Left, Right, Up, Down, Home and End navigation and selection commands.</li>
   <li>Multiple selection now works over word and line deletion commands, and line end insertion.</li>
+  <li>Left, Right, etc. navigation with rectangular selection is now allowed which completes "true" multi-caret editing support.</li>
   <li>When autocompleting with multiple selections present, the autocompleted text now goes into each selection.</li>
 </ul>
 <p>Other changes:</p>