If the settings file is saved, the editor warns the user what went wrong and where
When the editor automatically adds new settings to a file (due to upgrading), add a comment line that says something to the effect of "new in vx.y.z" so that the user at some point can then check out the new settings without having to scan the whole file.
Duplicate settings are highlighted
Not huge features, just some good (in my opinion) quality-of-life improvements!
Point 3 is duplicated in #1966. I'll close that ticket, but when it's time to work on this feature, please also take a look there as there are some nice suggestions from another user.
Borrowing some interesting ideas from Focus (https://github.com/focus-editor/focus):
Not huge features, just some good (in my opinion) quality-of-life improvements!