I believe you can force this to work if you disable the exclusive output control. This will allow you to set outputs simultaneously with CR outputs. Just make sure you’re aware of what you’re doing.
In the outputs pane, you have a stereo pair set as default monitor even though it is left unconnected. This constitutes your stereo output in the mixer. You can set up more however as I previously described.
Question is, why do you need to do this?