Nice work on the new release! Looks cool. Just 2 issues I've come across:
If you open the app and select your source and destination folders, the click the arrow down it throws this error:

It's obviously because no game is checked, but you might want to do "if no item is select do nothing" etc...
Second issue is if rescan, select the ISO on the top, click the arrow down, the button changes from green to yellow, when it should actually remain green since all you doing is moving the iso down the priority list:

Thanks!