I've just diffed it against the previous version and apart from a fixed whitespace, there's no other difference in saveactions.c 👍
I'll wait until the next weekend and unless anybody has some more comments, I would merge it afterwards 🎉
If you feel bored, it would be good to address https://github.com/geany/geany/issues/4033 - possibly as a separate PR so possible review comments don't block this PR. I think you don't have to go into too much detail and just describe the general functionality of this feature in https://github.com/geany/geany/blob/4264d0c507abc32c4e9f13aebaaec53d0c9e376b... (and possibly update the Instant Save section as the config is different now)