Multiple Percussion Instruments on One Staff

To use the same staff, and change instrument, see:
https://musescore.org/en/handbook/mid-staff-instrument-changes

But...
Using the above, will not allow a change between a percussion staff and a pitched instrument staff or vice versa.
So... create both a pitched staff and a percussion staff and use 'Hide empty staves' (e.g. so the pitched marimba staff won't display where the percussionist plays the snare).

You can edit a drum set to have as many or few unpitched instruments that you want. You DO want to use this feature for the percussionists who play, for example, the Snare drum, Ride Cymbal and Triangle. Pitched percussion cannot currently be put on the same staff as non pitched percussion, so you will have to make a separate staff for any and/or all pitched instruments played by a single musician. He can change instruments from say the glockenspiel to the tubular bells if you want using the same staff - they're both pitched.

Start by making two instruments, one an unpitched followed by a pitched. For examples sake, lets use the Ride Cymbal and Glockenspiel. Once the score is started for those two instrument, right click the Ride Cymbal and chose Staff Properties. You have one line, but will probably want more for more instruments. Adjust the number of lines you want on the staff and click OK. Next, right click the staff again and chose Edit Drumset. You can then add the instruments to the staff, assign note heads, lines voices and so on for all of the unpitched instruments.

See https://musescore.org/en/handbook/drum-notation for further info on editing the Drumset.

You can now double click any barline on the drumset staff and drag the box that will appear at the bottom of the line down to the bottom of the Glockenspiel staff. This will give the appearance that the two instruments go together. When the musician uses both staves rather quickly or even at the same time they will have to both be visible, when there is a long period of rest on one of the staves it can be hidden.

See: https://musescore.org/en/handbook/layout-and-formatting#style-menu for info on hiding empty staves.

If you need to change pitched instruments see: https://musescore.org/en/handbook/mid-staff-instrument-changes

Look through this and then ask specific questions and someone will be happy to give you further advice.

Anyone know if this is a feature that is in the works (i.e. combining percussion and non-percussion staves in the same part)? This is extremely common in orchestral music, as certain percussion instruments often only play for short periods and the player then switches to another. Some pieces combine all the "keyboard" percussion into one part, but it's impossible in others and so it gets split.