Hey there,
When I use OB, I have no function to the Main Volume knob on the AR, it only works without OB via Main Out.
Question at this point: is it possible to use the Main Volume knob in OB mode?
Or is there another function to fade in out the Main Volume in OB Mode?
Would be very nice to get some info from you 
Volume fader in DAW?
Yes you are right,
I found out that I could use my Push 2 to control the main volume via knob.
But I guess I would use not OB, the standard way via main outs and into the Mackie mixer seems more convinient for me at the moment.
But I will more explore the possibilities via OB.
Thank you for your reply.