I was about to create this request, but found that it already exists (not in Bugs, but in a Feature Requests category)
I recently almost lost a part of my note. I deleted a piece of text, because I was almost sure it was duplicated in my other note. Then I switched to other note to double-check it, but it was not duplicated😱. When I returned back to my initial note, and was unable to undo. Thanks to cloud storages like Dropbox/OneDrive which store multiple copies of a single file for recent periods of time. If I worked with bare file system, I would have lost what I removed.
There was also another episode when I mixed up with hotkeys and removed the whole content of a note and then switched to other note which led to content loss.
Missing undo for each file I work with during a session is really disappointing. And for me, as a software developer used to work with IDEs, it is also counterintuitive. Obsidian writes changes to notes when you switch between them implicitly, and at the same time does not allow to undo your work. Intellij (which I mostly work with) also saves files implicitly, but you have an undo buffer working until you restart the app.
So this improvement would be really nice to have.