Make standalone staves part of a pair of piano staves
Sometimes I import piano (or two-piano, chamber) works into Musescore from MIDI or MusicXML and then piano staves are stand alone.
I can't see a way to use the Instrument Panel to move a stave into a piano pair.
I've tried creating new blank staves and copying the complete original stave, but get a variety of problems e.g.
* Musescore reports that tuples cannot cross taves
* clef, key, and time signature changes midway through the staff are sometimes lost.