Hello,
Decided to share my UCCNC screenset editor with everybody here:
https://snapwebapps.com/uccnceditor/
It currently supports all basic functions of the built-in screen editor PLUS the ability to select, delete, move and edit multiple controls at the same time
You can also create button pictures.
Due to the limitations of the web platform you need to import both the screenset file and then the BMP/screensetname folder.