Very nice! I just downloaded the latest build and am already using several of the changes. I'll keep an eye out for the freezing issue, hopefully it's fixed.
In Tile editor would you consider swapping the right-click and shift-click actions? In YY-CHR, which is pretty much the best chr editor out there, right-click is select color and I keep on trying to use that in Mesen.
So shift-click would be set transparent and right-click for select color.
The other awkward key combination in Tile Editor is ctrl-up for flip horizontal. Definitely not intuitive. I had suggested ctrl-left/right for flip horizontal, ctrl-up/down for flip vertical, and then ctrl-
shift-left/right for rotate. Could use alt or some other combination as well. Either way, no biggie.
Btw, one of the features that's been very useful is Edit Tiles 2x2, 4x4 etc
from Tilemap Viewer. Awesome work there!