Sorry if I've missed something but why do you need these human readable files to be available but for whatever reason Joplin isn't the method to view them?
I had a look, there are a few things regarding automatic backups - Best method to backup notes - #2 by laurent and @JackGruber's Windows backup tool - GitHub - JackGruber/Joplin-Tools: Various Python tools for Joplin (Hotfolder, PDF Previews, ToDo List) and AutoIt (JoplinWinBackup) for Backups under Windows. but these aren't quite what you are asking. From what I understand they will perform a full backup of all of your notes, not just the ones you change. I don't know the about any potential dangers of either of these so use at your own risk.
Check the readme, it has a section on external editing.