Undo and Redo

Every property change you make - Fill, Borders, Font, Cell padding, renaming a style, deleting a style, and so on - can be undone.

• Undo: Ctrl+Z, or the Undo button in the toolbar.
• Redo: Ctrl+Y, or the Redo button in the toolbar.

There's no limit specific to this app on how far back you can undo within your current session.
Closing the file (see Closing a file) clears the undo/redo history - it doesn't carry over to whatever you open next.