Return groups are separate, but linked to product groups. Return groups hold various settings that, based on the product group that is linked to it, decide how the customer needs to proceed with the product. Return groups are unique per return type and have a variety of settings and configurations.
Creating Return Groups
Return groups can be found under Settings > Return Type > Product Return Groups. Creating a return group enables it for that return type, making it possible to link that return group to a product group.