I suppose you could say that we want to make some of our own custom Categories. The DNSFilter pre-made categories can seem arbitrary at times, or overbroad, so being able to make our own custom category would be helpful for managing content filtering whitelists or blacklists.

Regarding "by vendor", I grammatically overlooked that part of the request, and projected my own idea of a way to make a custom category for grouping domains that make sense to me.

I'd like to understand this request better. What are common vendors that you would anticipate "grouping" in this scenario.

Sounds like a winner to me, to have a whitelist of a group of Domains. Even better, would be the ability to use URLs, which DNSFilter can't do now.