You can now assign a Customer to up to 500 Customer Groups; previously, Customers could only be assigned to one Customer Group. You can hide the legacy single Customer Groups assignments in the Merchant Center by navigating to Settings > Project settings > Miscellaneous.

Additionally, you can search for Customers by their assigned Customer Groups with a new filter, Customer group (Assignments). You can use the Customer group (Assignments) also as a predicate for Cart Discounts.