Today I seemingly lost 2 days worth of my notes, all of which I keep in a single file/note (for a given month). Through the history feature, I was able to restore a "previous" version of the file that had the lost data. So basically, the history looked like:
A -> AB -> ABC -> ABCD -> A
So I added things to the file and at some point, a "newer" version in the history appeared without the latest edits.
This may have happened when I synced on multiple devices. I didn't actively use Joplin there, but I did wake another linked device from sleep for a couple minutes.
To debug this further, the first thing I would want to know is which machine wrote each of those versions. My suspicion is that A -> AB -> ABC -> ABCD were all written by my main PC and the final A was written by that other machine.
So my feature request is to make this information part of the history metadata and to display it in the select box where one picks the past version.