Hi José,
It's one of the high priority features for me. My idea is to let users put screen files into a special directory which will be automatically loaded into the palette. This way if you want to do some changes to the palette you can just edit these screen files.
Other idea is to allow multiple widgets in one screen file. This way a palette category could be created using just one screen file which has all the custom widgets inside. I am still working on fleshing out this idea.
Please let me know what you think.