play instruments that are not in the current part – Musescore 4

I use MuseScore 3 to prepare sing-along practice recordings for individual parts for my choir.
I create excerpts (parts) with the voices but without piano, but record the practice files with piano. For this I used the “Play part only” (off) switch in the mixer and was able to set the piano properties.

This is what I miss in MuseScore 4: I can see every instrument in the mixer, but I can’t unmute the piano in the current part. (M(ute) Button is disabeled, S(olo) Button mutes only other voices).
Is there a way to play back instruments that are not in the current part?

Musescore 4.1.1 Windows 10