Minifuse 4 and subwoofer control on output 3 and 4

I just bought the Minifuse 4 and I’m having a bit of a brainfart.

I have 2 KRK monitors and 1 KRK 10.4 sub. I’d like to connect the sub to outputs 3 and 4 so I can control its volume independently depending on what I’m doing. However, the issue arises when I use my headphones (e.g., during mastering). The main dial on the Minifuse only controls outputs 1 and 2, so the sub on outputs 3 and 4 remains active, even when I lower the main dial to zero. To mute the sub, I have to manually open the Minifuse interface and mute outputs 3 and 4.

Alternatively, if I connect both the monitors and sub to outputs 1 and 2, I can control everything with the main dial. But in this case, I’d need to manually adjust the sub’s volume or use its footswitch to disable it completely.

Is there something I’m missing here? What’s the best way to set this up?