The Undo command can apply to the following actions:
In Style Editing mode:
Property settings
Rule changes (creation or modification
using a wizard, enable/disable)
Cut or Delete operations done using
the Rule Menu
Selecting/clearing an option in the
Options dialog box displayed when you choose Edit>Options
In Diagram Editing mode:
To undo one of these actions, choose Edit>Undo.
There are unlimited levels of Undo.
When you have undone an operation, you can redo it by
choosing Edit>Redo .