See also:
To undo/redo actions within the Letter Writer:
To undo the most recent action, either;
Click the Undo button on the toolbar, or
Press CTRL+Z, or
Select Edit > Undo from the menu bar.
To redo the most recent undone action, either;
Click the Redo button on the toolbar, or
Press CTRL+Y, or
Select Edit > Redo from the menu bar.