I can't find the abandoned-cart feature in my panel — does it exist?

It does — Marketing → the 'Abandoned carts' card, under 'Bring them back'. It opens straight onto its own section: turn it on, choose how long to wait and what to say; every prepared message then waits on the Marketing review tab for your explicit approval, permanently — abandoned-cart messages never auto-send, by design. If you don't see the card at all, it is part of the promotions plan features.