I came to the forum looking for the answer to this exact question. I thought I was being dumb in not being able to find something which must *obviously* exist in kit so beautifully designed...
Option 1: Powering down speakers is extremely clumsy and awkward, to achieve something so simple. Option 2: Disconnecting main outs doesn't work when my speakers are all connected via L6link
So, @steverubble did your idea of creating said Scene do the job? Like you I don't use them (yet) and am looking forward to seeing up my pa too test your idea. Thanks!