To undo a mistake, you can either click the Undo
button on the toolbar, or choose
EditUndo.
To redo an action, you can either click the Redo
button on the toolbar, or choose
EditUndo.
Redo puts back the change that you reversed by using the Undo option.
Undo and Redo are relatively new features, and while the
implementation is
quite good, there are still some actions that cannot be undone.  Its
always a good idea to save your work before making any modifications
that you're not sure you'll want to keep.
