Playback when mixer window is open?

Is there a reason for this:
When I am in Play mode and open the Mixer window (F3) I can’t start playback with or the playback arrow. So far the only workaround I found is clicking on an “event” in the drum track.

Is there quick way to mute an instrument without going to the Mixer?

MacOS Catalina, Dorico 3.5

You should find that you can start playback with Space or with P. Does that work?

You can quickly solo an instrument via Play > Solo Selected Instruments, but I’m afraid no corresponding command exists for muting instruments.

I have not tried the “P” shortcut. Spacebar seems to start playback but it is not actually starting to play back until I click an event in the drum track.

Solo button works, too. I was trying to hunt down a strange ping sound and couldn’t tell which track it came from.