Editing instrument properties
Editor that could add properties (technoques, sounds, MIDIes) to file instruments (or into the score), create couples of instruments for ones stave - clarinet player changes clarinet with saxophone but has sill one staff. The same is SOLO and TUTTI in any stave of SATB. And many similar occasions.
Some instrument have possibility to change sound (mute, flageolet, and more special techniques). Musescore has instrument library in special file. There is described each instrument and also its sound particularities. But this file does not reflect all of particularities. For example harp can play "sul tavolo" (sound like guitar) or "flageoletti" and in basic library this properties are not. But if you open the file instruments.xml, you may find harp and add these properties (as did me in attached file). But special editor would be much useful and safer.