How to expand a Consistency Group?

We have 2 Unisys mainframes in different locations with  good link between them. We're testing Unisphere for recoverpoint v4.0.2. We defined  CG with a single LUN. UNisys mainframes have fixed size volumes of 9GB, but multiple volume families are common and, because new physical units can be added and even subtracted on the fly, we expected REcoverpoint would also.  But, as far as I can see, this isn't supported, at least in the GUI.

Is this correct?   If not, how can I add a source LUN and target LUN to an existing CG?   Or, delete a LUN? 

Just to be clear, I'm not talking about the journal.

Thanks