Thanks so much! I fixed a bunch of stuff you mentioned in the latest update :)
I think EVENTUALLY it would be nice to add other exports like c64 and nes/SNES/genesis, but it'll take some time to get there for sure 😂
You can import images by clicking the file menu - import. You'll be asked for the file and then prompted what to do with it (new scene, new layer, as a palette, convert colors, etc)