Admin walkthrough — show only to some customer groups

1. Make sure the customer group exists in Customers → User Groups and the right customers are in it.
2. Open Vendors → Vendor Visibility and find the vendor.
3. Switch them to Hidden.
4. Under Allowed Usergroups, pick the groups that should still see them.
5. Sign in as a customer in that group and check the products appear in listings; sign out and check they don't.