Sub-Groups

Sub-Groups
Currently, each customer is a group.  This works well enough.  
Some have a great many endpoints. 
Would be great if I could Sub-Group "Accounting" under "Customer-1".

They could read like:

[Customer-1.Accounting]
  AcctReceivable
  AcctPayable
  Invoicing
  AcctMgr
[Customer-1.Production]
  South Mix Room
  North Mix Room
  Dry Room
  Prod.Manager

Any addition in this direction would be appreciated.