Wonderful!
This is not a problem to use an external editor for maps and sprites, it is even better since we can use very good dedicated programs like aseprite without any problem.
No need to bother with exporting individual tiles or some special format since GB studio recognizes automatically the tiles from the PNG files!!!!
The music editor also allows for 4 tracks which is enough to make good music.
I have tested bitsy and pulp, rpg maker, pico-8 and a bunch of others but GB studio is the one that is the easiest to make completely original content without bothering with import/export problems. It has the best balance of all the 8/16 bit game maker platforms around!!!
Keep up the good work!!!! (a better/compact interface for the events would be easier to see though)