Having another card within a control group card.
Example of how it is now:
Card1 - Bath 3
Card2(within Card1) - Plumbing Fixtures
Card3(within Card2) - All Fixtured Offered
Idea:
Card1 - Bath 3
Card2(within Card1) - Plumbing Fixtures
Card3(within Card2) - Gibson Series
Card4(within card3) - All colors, models, and prices for those
Card3(within Card2) -Eva Series
Card4(within card3) - All colors, models, and prices for those