Dear community

I have an active speaker system plugged via XLR and headphones via the phones connection and I'm wondering if it is possible to set the volume of the headphones to "line out" strengths and only control the active speakers via the big volume knob.
Music should always play on both outputs. In case I don't need the active speakers I could simply turn down the volume while my headphones still work. I have an Adam active speaker system and my sub-woofer doesn't have an on and off switch, otherwise I could simply turn off the speakers.
I know I could enable the toggle phones/line out function in the setup menu and then switch between the 2 outputs by pressing half a second on the volume know, but I'm sharing an apartment with not so technical people and I want to make things easy.
Basically the headphones (they have their own on/off switch) always work and speakers can be controlled via the volume knob.
Hope someone came across the same wish and was able to fixed it.