Does maintained status let me leave and re-enter Canada while my extension is pending?

No. Maintained status only protects your existing conditions while you remain physically in Canada — it does not extend to travel outside the country. If you leave Canada while an extension application is still pending, maintained status ends the moment you depart, and it does not automatically resume just because you come back.

Re-entering Canada afterward depends on satisfying a border services officer that you qualify for a new period of authorized stay at that point, based on whatever valid documents and circumstances you actually have, not on the fact that an application was already in process before you left. This can put someone in a considerably weaker position than simply staying in Canada and waiting for the extension decision, particularly if their original supporting circumstances have changed or their documentation is not straightforward to reassess at the border.

Anyone with a pending extension or restoration application should think carefully before travelling, and ideally get their specific situation reviewed first, since leaving can undo the protection maintained status was providing and is not something that can simply be undone after the fact.