The typical undo and redo actions are available in the Edit menu:
Undo
Ctrl Z (Meta Z on OS
X)- Reverses a maximum of 200 editing actions (configurable in the Editor preferences
page) to return to the preceding state. Note: Complex operations like Replace All or Indent selection count as single undo events.
Redo
Ctrl Y (Meta Shift Z on
OS X, Ctrl Shift Z on Linux/Unix)- Recreates a maximum of 100 editing actions that were undone by the Undo function.