A device can't be in two masking views on the same set of ports to the same initiators.  The device would then be mapped twice on the same port with a different lun address to the initiator.  This would lead to a lot of confusion for the host.  I've never tried this, but probably the only way to do this would be to zone the host (temporarily) to two additional ports.  Then create the cascaded SG as desired and create a view containing the parent SG, the original IG, and the new PG.  Once the devices are visible to the host on the new paths, and your multi-pathing software recognizes them as the same devices on new paths, you can delete the original masking view.  After this is done, add the original ports in the new PG. Confirm the devices are again visible on the original paths, then remove the temporary ports from the new PG.  You may want to test this approach before attempting it with production devices.
Hi  We have a little bit embarrassing situation in a VMAX environment:   Example:  Original situation:  mv_fabricA sg_original pg_fabricA ig_fabricA mv_fabricB sg_original pg_fabricB ig_fabricB  Create sg_father sg_child1,2,3,4...  If try to create a new masking view :  mv_fabricA1 sg_father pg_fabricA ig_fabricA  System informs me that the device is already masked and cannot duplicate masking views.  The only way that i can do it, is deleting masking view mv_fabricA and inmediatly create mv_fabricA1. During the process, the host will lose access from fabricA but will do it for fabricB.  Has anyone other idea?  With regards
Reorganize Storage Groups