Redoes the last undone editing operation.
procedure Redo;
(Introduced in version 1.3)
This method does nothing if there is no operation to redo.
Information about the operation to redo is returned by the methods RedoAction and RedoName.
This method must be called only when the document is formatted.
This method is called when the user presses Shift + Ctrl + Z ( Shift + Command + Z on macOS) or Shift + Alt + Backspace .
Method type: 
editing-style.
See also:
▪Undo;