I have no Gog's Redout yet and any Vive headset to test this, but try this.
In the properties of added game, set as in the picture, "Launch options" to "-vr", and you can add this to VR Library.
Please provide feedback, as I am interested if this works.
Edit: Just to make sure, have you tried with the first method in this thread, before trying through Steam? Redout developer says it has "VR Support - Oculus Rift, HTC Vive or Razer OSVR".
Post edited June 21, 2021 by kubapl