Exactly what it says on the tin.
Take e.g. https://beta.bookbrainz.org/work/f591f6b6-6df8-4175-ac22-0ee13eddce0c which I've added to an "owns" collection - after I do this there is no visual indication that it even is in a collection, and the action to add to the same collection can be performed again without any indication that it already is in a collection

Ideally we should have "part of # collection(s)" text somewhere (possibly as a link, to a (tab) page with a list of all collections with owners (and a text of "also in # anonymous collections") like on mb: https://beta.musicbrainz.org/release/f82e3a9d-5f8c-4214-aaa4-32c82a0cebc1/collections )

also take a look at all the data shown in the "collection view" list https://beta.musicbrainz.org/collection/0d804e65-939a-42bf-baaa-8b0d03021f52/