I suppose the easiest way to be able to install multiple files would be to slightly
tweak Frescobaldi’s code (which can easily be done on a distributed copy as it is python).
For this find the location of of the frescobaldi_app module and open widgets/schemeselector.py.
[....]
I found the file and tried to modify it. Unfortunately I have a (pre)compiled .pyc file so I can't modify it directly.
Now I don't have time but I'll try to find the source and compile it (hopefully I'll be able to do it).
Thanks a lot!
Gianmaria