I've spent a lot of time developing this editor on my free time, and it is mostly usable for the most part. I got to create a complete Quest level with it without having to use the official editor.

It does offer almost the same feature as the official one, except that there's also a new few tools like auto-symmetry tooling and it kinda act like one of those pixel art program where if you draw on the left, it draws on the right side and vice versa.
It also has a lot of in-game elements than what the official editor could offer, necessary for other elements for Quest map. If you want to give it a try, here's a link to that editor:

Github Link: https://github.com/Terria-K/Towermap