After purchasing Capture One Pro 10 I again tried setting up my Canon 5DS R so I could tether via USB3 to my laptop, and at the same time tether to a TV monitor via the HDMI ports on the camera and TV.
I'm happy to report that it is working just great. When I select the camera to live view I'm able to see the live view display on the TV. Only problem with that is that it disables live view on the camera itself, so I have to watch the TV screen to do any manual focusing. If I turn on live view via Capture One I can focus using the laptop if I prefer. Turning live view off on Capture One sends the live view back to the TV.
At the same time I'm able to tether the camera to my laptop using USB3, and capture images to Capture One. So now I can move around the studio adjusting lights while I monitor the adjustments on the large TV screen, which saves me from running back and forth between the camera and lights to see if I'm achieving the lighting effect I want.
So the setup is: TV to camera via HDMI, camera to PC via USB3, turn on camera live view, capture images to Capture One Pro 10.
Note to Canon users: If you shoot in manual mode with studio strobes you may have to disable exposure simulation in live view, otherwise the live view screen may be too dark to see.
Thanks to all for the help.