Ajbelayer,   As stated previously, the Online Capacity Expansion can't be done from the controller BIOS, it must be performed via OpenManage, the Dell systems mgmt software.    
I recently replaced the 4x8TB drives with 4x18TB, one at a time letting the RAID 6 finish rebuilding between each,, everything worked great during that part.   The problem is now I cannot access the additional 10TB per drive to create a extra VD with the additional space, the controller claims there is no free space to create a VD. Firmware and driver versions:   How can I access the new space of these drives?
Drive upgrade with PERC H710 (R420 server) issue