I know on the Qu16 it did not have DCAs.
I had to patch the Alt out to the 2trk return input to develop my my own LR mix to all the other mixes.
I thought the Qu5 had added VCAs. What am I missing??
The Qu-5/6/7 (and Dante variants) all have 8 DCAs each.
But,
I had to patch the Alt out to the 2trk return input to develop my my own LR mix to all the other mixes.
This isn’t what a DCA is for (it’s for controlling inputs together - no audio passes through it). You can’t patch a mix into another mix. You can patch mixes together with a Matrix, of which the Qu-5/6/7 series has 4 - you can pair these into two stereo pairs if you want.
Qu-5/6/7 has the option to turn your auxes into groups, so you could group everything into a “main mix group” that could then be sent to the auxes and main LR as a single entity.
Possibly the best way to answer would be to ask…What’re you trying to achieve?
A DCA is very much what old analog mixers might have called VCA. It only groups collections of inputs or mixes and controls level, creating a sub-master fader. Suppose you have a drum kit, with a mix of various mics. You can send the whole kit through a DCA to control the whole kit level.
I’m sorry, I meant Matrixes not DCAs! 
A&H have gone to the trouble of creating a dedicated website for the QU-5:
https://www.allen-heath.com/hardware/qu/qu-5-qu-5d/
There you will read, among other things:
You can there also download the user manual, which describes everything in more detail:
Actually the QU16 does have DCA groups, there are no faders assigned to a DCA on either layer. To set them up first you need to assign the DCA’s you need in the center custom layer they are also on the Qu Pad app.
There are no audio groups on a QU16.
Thank you SQuser! I know the Qu16 did not have a matrix function.
I didn’t write anything about the QU-16 here, but only regarding your topic. )
Sorry it should have been posted in the main body of the thread.
QU16 does have DCA’s, QU-5 has DCA’s.
QU16 does not have audio groups or matrix mixes, QU-5 does have audio groups and matrix mixes.
What kind of routing do you want to do.