@ XoeoX
Until your request is implemented, here are 2 ideas for a possible workaround, which I cannot try out myself.
Couldn’t you perhaps use your 4 DCA groups as additional mute groups?
If you use the “Mixing Station” app, you could certainly create a layout in which the buttons of these 4+4 “SIP groups” are right next to each other.
Theoretically, you should also be able to use the IDCAs from “Mixing Station” for your project by creating an IDCA for each of your SIP cases that leaves the desired channel unmuted.
Here, too, you would only need in the layout the corresponding mute buttons of the IDCAs.
But sorry if I’ve thought wrong.