Submitted by charles.a.braun on September 21, 2018
It may have been there before but I just noticed it today, for the first time.
However, last night I updated to 2018.36.2 and now there is a new icon that (seemingly) randomly appears on the screen directly below the AP icon. I can tap the icon and and X goes over it to indicate muted and tap it again to turn off the mute. I was not using Nav at the time so not sure what it does, but taping it had no impact on the stereo or its volume.