Undoing and redoing actions
You can undo or redo the last set of actions that you performed while working on your movie.
To undo the last action• Click the Undo button 
on the Toolbar.
on the Toolbar. To redo the last undone action• Click the Redo button 
on the Toolbar.
on the Toolbar.
You can adjust the number of undo levels in the Preferences dialog box.
You can also use the keyboard shortcuts [Ctrl + Z] and [Ctrl + Y] to undo and redo actions respectively.