I'd add that unlike the player, it might be best for the editor to always do application DPI rather than make it an option. As I recall, the only reason we want it as an option for the player is for performance reasons. (Although ideally we should try to address the performance issue so people don't have to compromise between blurriness and bad framerates.) The editor doesn't seem like it'd have the same performance demands as the player.
The editor actually seems like it's pretty close, most of the UI seem to manage to retain more or less the same positions and dimensions when you compare the two screenshots. It's just the width of the left panel that seems to be affected causing part of the UI to get cut off. So maybe there aren't even that many things that need fixing with application DPI.
On that note, @WillLem: I'm guessing it'd be very helpful if you can look through all the other UI in the editor running with application DPI, and post screenshots here of any other that have similar problems like things getting cut off or horribly mis-positioned and/or mis-sized.