I only own a sq5 so I cant tell you anything on the encoder thing…. But I think it should be possible or it should be made possible because its a good function for custom encoders…. Should be possible tto route every bus master on a custom. If its not post it to feature request because its a real basic thing for custom.
But you can assign your auxes to a mute group and the mute group to custom button.
Select the Bus and go to Routing. Tip the Mute Group part of the channel strip in the display and assign your aux to a group. Then you go to the custom button settings. Choose the button you want and adjust the mute group you selected to it. Dont forget to click apply on the touch for saving and rememeber that you have to make the buttons recall safe otherwise could happen that you will have to set the buttons again
