Is there any way to setup a channel on the QU series where the channel source is from the oscillator (50hz) then, set the gate of this channel so that it triggers from the main kick drum channel to produce a fatter kick sound when using both together?
AFAIK no. Fattening a kick drum using the oscillator would require the gate to be able to key listen from a source other than “self,” (ideally with a post-fader tap) which the Qu series does not allow. You’d also have to be able to route the sig gen’s signal from the assigned bus to a channel (the buses don’t have gates,) which the Qu doesn’t allow internally: you’d have to go out of the desk and come back in.
Makes sense.
I stopped by the church tonight where I’m the full time FOH engineer and tried this on the Digico SD9. So easy. Worked perfectly. But, the Digico is a pro touring console as well. Not a fair comparison. I own the Qu32 as my personal gig board.
Thanks for the conversation!
slightly off topic but may I offer some advice,?
you want to use 50 Hz. to fatten the kick drum.
It would be imperative to me if I were doing this (but I never would because there are much more natural better ways to fatten a kick) every drum is tuned and has a root pitch. Many drummers are good drummers but have never learned how to properly tune drums, but many have though, and regardless, the kick drum has a root pitch, and whatever that pitch is (that day or week) is the “exact” pitch you should use from your frequency generator if you want to proceeed with your way of fattening the kick.
Just my penny’s worth 
True the sd9 is an awesome console and it’s no surprise it can do it, but the X32 can also do it, and they’re leagues apart.
As dpdan said, 50Hz is just a starting point, it’s not set in stone. You can use a different freq if it sounds better. Using a sub harmonic synth as an insert could also work. I know it’s not on Qu, but it’s on gld.