My solution needed an external script to update the rules dynamically. The manpage for nftables is very terse and a lot of times assumes that the reader has some previous knowledge, that’s why I gave up half way. Meanwhile the wiki didn’t have an answer to my problem at all.

I am not saying manpages or wikis are bad, by the way. But in terms of specificity (when your problem is really niche), DDGing/StackExchanging > Wiki > Manpages.