4.7.1 Undo

Syntax: Undo [n]
Abbreviation: U

undoes the last n actions. If n is not specified, it is assumed to be one. After you undo a number of actions, you can Redo all or some of them; see Redo. However, if you take any new actions after having Undone some, you can no longer Redo those Undone actions. See Redo.