Interesting, I find it useful. A couple of features you could think about:
1. Is there a feature to create a "pull request" to the collection maintainer to propose adding some extensions to their collection? Otherwise, there would be several public shared collections for the same use-case and it may become scattered.
2. I'd like to be able to favorite / like / star a collection, and that to be used as a signal to search results ranking.
Another adjacent domain to expand could be Tampermonkey scripts.