Substitute instrument

I'm looking for a way to duplicate a part within my score so that I can use a substitute (on a different instrument) to cover a part. Specifically, I want to duplicate the horn part in a brass quintet to turn it into a flugelhorn part (with appropriate transposition and range adjustments).

I'm a Finale refugee. In that program, I would simply save the horn part (a separate file from the score) under a new name and work on the resulting file. But in MuseScore, the parts are embedded in the score file, so I'm looking for the approopriate methodology in this new world.

Thanks for any guidance.

Will