Awesome Program, the 'export no$gba' feature is a HUGE time saver!
Though it would be nice to have the default value for the name to be "DSI-1.mmc"
One small suggestion, It may be helpful to put a few warnings in the program.
For example, if the user loads up a dump, downgrades, then asks to save as a decrypted dump, maybe say "saved decrypted dump, DON'T Flash this!"
Also a message for saving the no$ file as 'nand_dsi.bin' "This is not a flashable file.
These are more for new people, so it would also be nice to have the option to disable these messages.