Keyboard Shortcut: Ctrl-Z
Undo "undoes" the most recent change. If greyed out, there have been no changes to reverse. Note that some changes cannot be backed out using Undo. There are some changes that do not support Undo; remember that if you need to recover to a prior save or major change point, you can open the Design Version History and open a prior version.
Keyboard Shortcut: Ctrl-Y
Reverse the most recent "Undo".