I already intended to consider only the last update, just like normal multiple undos/redos behave in applications (edit: re-reading your reply I realize now you already had understood this - or maybe not - I’m unsure).
Your idea of a drop down and only undo delete actions is good, but I’d prefer a normal multiple undo/redo feature as explained, it’s more linear and straightforward for user, and we’re just addicted enough to this way with other desktop and web apps that it would be somehow confusing for some users to use smoothly a never-seen ever feature.
I’d also like it to do not only deletions, but also creations and updates, because sometimes updates can mess up things just like deletions. Creations could be omitted, but I prefer not just because it’s simpler, and linear, and avoids to confuse the user while going backward and forward into an history line.
So, just like that:
action 5 <---
...whatever "action x" is (deletion, creation, update, of document, of chunck, of snippet...)
This way it would work even if future version of MODx will introduce some other thing like tv’s, chunks, etc. (the Auditor would need adaptations, but not so much its undo/redo feature.)
Thanks for taking my proposal into consideration for future versions of Auditor (of course even if you want to go with your way: you’re the boss on it