Unfortunately the mastermind doesn’t really function well as a looper controller, and I wasn’t able to find a midi controller that functioned well as one with the h9 while doing presets/cc messages at the same time, so i use the aux controller mainly as a looper controller, (Stop, Reverse, Record), but is it possible to control multiple H9’s with just 1 aux controller?
Look at the XMT CC mapping. It lets you map an aux switch to CCs that the H9 will transmit. I don’t think it’s available via H9 Control, you’ll have to dig into the menus on the box. Then you’ll need to map the CCs to your desired functions on the receiving H9. I have an aux switch mapped this way to toggle active/bypass on 2 H9s, works great.