Can I undo a cleanup, or should I back up first?

There is no undo. Each task executes a real SQL DELETE, so removed rows are gone permanently — the module keeps no recycle bin or restore point. The run-all action is shown with an unrecoverable-action confirmation for exactly this reason.

Always take a database backup before your first cleanup. The screen shows the exact count for every task before you run it, so the safe workflow is: review the counts, back up, then clean one category at a time or run the full pass once you are confident.