I know that you can access to background list by just double-clicking it, but why would want to search for a name for a background instead of picking it with the background UI? My suggestion is remove the background list and replace it directly with the background UI.
2. Bigger "Script Editor" window by default.
Thanks for making it resizeable! However, now everytime I open the editor I have to resize the script window because it's too. Can you please make this window bigger by default? (a size like it used to have would be enough)
3. Resizeable "Variable" list (vertically only):
Sometimes I have too many variables and the limited size of the windows becomes a problem.
4. In the NPC Editor UI, move "Scripts" at the very end.
Since "Hold Generator" function is not used as often as "Scripts", I suggest switching their places; being "Scripts" at the very end and "Hold Generator" behind. This way when you scroll the window until the end, you know you will find "Scripts".
5. Being unable to delete Player's position.
Sometimes I'm deleting various objets and I accidentally delete Mario's startpoint. I suggest doing something like in Mario Maker; you can't delete it and if you touch (in this case, click) the player with the eraser, it shows it's ducking anmation while shakes a bit (horizontal shake). Ideally this happens only while we keep holding left clck and are using the eraser.
6. "Always on top" option for windows
- Alternative A (by right-clicking the window panel):
Alternative B (add a "pin" icon to the window)
Every time you click the screen, the tileset tab dissapear and you have to re-focus it, which can make the editing process a bit slower. That's why I'm suggesting this option to preventing this window losses the focus after clicking the level.
7. "Drag & Drop" objects in Tileset Editor.
- Like in PGE. (You can also drag & drop objects you already placed in the tileset)
Because it would make the things much easier.
8. Updating windows.
I leave this suggestion to the end since I don't know how hard it will be to achieve. There are some "old" looking windows ("XP" windows) and some "modern" ones (the ones that fits with the operating system:
"old" windows examples
"modern" windows examples
Would it be possible to update these "old" windows to make them look "modern" as well?