I tried selecting all or dragging over the channel strips in the Mixer Window, and hitting the mute button. That works. Thx. Command, Option, and or Control clicking a mute button doesn't select them all as does Command click in the Arrange Window. I have noticed, however, that if there are say four channel strips in a group and you Command click in the Mixer Window, it will mute all of the grouped Channels. Interesting, but not a total solution.