We can see the features for Subset Groups, now we just need the OOTB feature to work. For example, we could use a subset group for combining subsets for "Canada" and "Company1" into a subset group, so that we can assign Canada catalog to all Canadian customers while also assigning a few customer specific items.
Menu: CIMM2 / PIM / Subset/Catalog / Subset Groups
Thanks Sabrina for the idea, we will look into it and will get back in case of more details required.