You don’t need a secondary Group Channel. Create just one, put the VST Connect SE Cuemix plug in there and use sends to transmit whatever the Performer wants to hear to that channel. It’s simple: the cuemix plugin sends whatever it gets to the Performer. You (engineer) don’t want to hear this yourself, so lower the volume of this one Group Channel to zero but don’t mute it. It may also be vital that this Group Channel is sending to the Cubase Master output even though the engineer doesn’t listen to it because of the way delay compensation works.