Ability to select Aux / Flex Mix Masters in a DCA group

I'd like to have Aux / Flex Mix 12 Main seen in my DCA Group Selections. Am I missing something. I do not see anyway to select Flex Mix Masters as a selection from the DCA list. Only chaels 1-32, FX Ret A, FX Ret B, FX Ret C, FX Ret D, Aux in 1, Aux in 2 and Tape in.

Would be nice to add a DCA group with a Flex Mix Master. Any ideas?