With standard processes you can revert back to a previous version via the change log. That option is not available for variations. I'm not sure why. It should act as any other process.
ADMIN RESPONSE
Sep 7, 2022
We’ve made some significant changes to how process variations work in Promapp, and we plan to release this at the end of June.
Thanks for getting in touch. We may look at this as part of our overhaul of our process variation add-on. We'll monitor this idea for other client interest.