I would really like to see music add-on where you can select the types of music files you have (.mp3, .ceol, .wav, etc.) so you could add tracks to rooms and perhaps even when you have an item?
I would also love to see a bit of module-ing of the painting module, due to if you have a lot of different areas in the game you have a lot to scroll through. So perhaps adding a little "file" button would be nice to where you could put some paintings in files that are right for you! (and possibly a "mother" file that still has everything there for you).
Also adding in a "shortcut" module that would allow you to do short cuts, like being able to right-click while painting in a room to select the block that you were painting over. There could easily be other shortcuts added too.
Sadly I don't know much other game making engines,the closest thing I know about and used a bit is "Minecraft World Painter" and "Valve Hammer Editor" (which hammer is really not known for user friendliness) so I sadly don't have something interesting for you to look at.
-however, if you really want stuff to do with the dialog boxes to make it easier. Making the areas between them greater, or add a small button under them, I say this due to me not realizing you could add more dialog in the shuffle forever.