Since vMix Calls are routed N-1 (mix minus 1), it should be possible, also to add a talkback channel to each call.
When we have several calls on a meeting, we sometimes need to check with the others, if their audio is good and anything went well, before they go on air with a 30 min statement. For now, we need to script this with companion, activators, shortcuts,... Could this be a simple button on the audio mixer?