Hosts such as cubase , Logic , etc , operated with Asio driver , cannot support two cards at the same time . This should be done at the hardware and or driver level if the manufacturer has implemented it to the product. Gina has that feature, but it can only be connected internally with another Gina or Layla and NOT a Mia card. You don’t specify if you have Gina 20 or Gina 24 bit . So if you have Gina 20 and want more I/Os selling it to get something more contemporary and expandable such as RME hamerfall DSP with multiface could be more useful than trying to expand the old Gina.
If you have newer Gina 24 that incorporates Adat optical I/Os you can easily add an external AD/DA converter with 8 I/Os from RME, Alesis , Behringer and others and have a total of 10 in and 16 outs. But external digital gadgets can add Jitter if their design or cable connection quality is not appropriate.