Maybe through autosave? If your editor makes a commit every time you're inactive for longer than X seconds that should solve that, which I'm pretty sure is how most editor undo stacks work at some level.

I just tried it in Nextcloud Notes on Android (FlorisBoard has undo/redo buttons), and it seems to work this way. If I type a bunch of words quickly and hit undo, it removes all of them. If I stop for a couple seconds between each word, it undos them one-by-one.