YES!!! i was about to make this same request just like you!
I was thinking that we can use the USER button on the Fat Channel secction to select those 8 buttoms not just to turn on/off the gate/limiter/compressor/etc, we can use those buttons to create differents Mute groups like the other mixers.
I think is a good idea to have this option in this compact mixer:
1. Press User Button
2. Select the Button in the fat channel
3. Select in the screen "Mute Goup"
4. Then, just like the 24 or 32, press and hold that button and select the channels that you want to Mute.......WABAN!!!.
We could have 8 Mute Groups in the Fat Channel using the USER button!