Cool, yeah it'd be great to have more tools to manage these lists. Keywords are also something that relay.tools supports in lists, though I don't think nip51 has keywords 🤔. I'd also be very happy to accept ideas and modifications to relay tools, it's opensource and I could help you get a development env setup if you're interested.

If you want to see the current state of things and sign up for a testing relay I'll refund you the sats. relay.tools, GitHub.com/relaytools