Undo (Ctrl+Z)

The Undo button is normally inactive, and the adjacent drop-down list is empty. Once an action is taken, then the Undo button becomes active and the taken action is listed in the adjacent drop-down list:

The Undo drop-down list grows with each new action. You can click the Undo button to undo the last action.

Redo (Ctrl+Y)

The Redo button is normally inactive, and the adjacent drop-down list is empty. Once an action is undone, then the Redo button becomes active and the undone action is listed in the adjacent drop-down list:

The Redo drop-down list grows with each undone action. You can click the Redo button to redo the last undone action.