Selecting Expression CV output for a Keyboard:
This is unfortunately disabled – if you hit the aux button in order to select an output, it declares that it’s EMPTY.
So – you have to disable the keyboard group (set the FUNCTION to FREE) then select the aux output to your desired position.
Then re-select FUNCTION to KB. The aux output selection will be retained.
This is hardly a slick operation. The aux output parameter should be available whilst KB is selected in the FUNCTION menu.
I think this qualifies as a bug.