Instrument names on Instrument Change
I have a score with first movement having two horn (in D and E.) Second movement has two horns but the E horn is now an F horn. Third movement reverts to D & E. I experimented with a test scrore and when I went to staff properties to change the horn from E to F, all the labels for the measures preceding the instrument change displayed the new names. I did not check to see if somehow the instruments were also changed. So what is the best way to handle this situation other than adding a third horn to the instrument list and then one of the horns will not be played in selected measures. Not sure I understand all the comments in the documentation or some of the related comments in the forums for instrument changes.
Comments
Use an instrument change ( see https://musescore.org/en/handbook/3/mid-staff-instrument-changes#add-in…). In fact you will need two, the first to change the E horn to F and the second to change it back to E. The instrument change takes care of the change in labelling as you want.
If you change the staff properties, that is a global change - for the whole staff - unless modified by a mid-staff instrument change.