I'm not sure because I'm still new to kbin too. I'm also on kbin.social which is already big and people have already subscribed before to many of the magazines. So far it's always worked for me to use the search bar on the Magazines page, and just type the name or part of the name of the Lemmy community. It's kind of nice too since it'll show all existing communities/mags, and number of threads made, number of kbin.social subscribers.
for example I just try to type "anime" to find subs like that, and I tried "seattle" and could find it, but I'm guessing it's because you did that work just now to be the first subscriber on kbin.social?