How do I control the downmix sent to the headphones in the Control Room?

I don’t see where to control the downmix sent to the headphones in Control Room. I am mixing in 7.1.4 and I would like to manage what stereo downmix I am hearing.

that doesn’t work as you think
there are some tutorials available…

You really elucidated that for me.

did you configured a downmix preset?
If you did, click on it’s button…