Lens is partway there, but CSE is significantly more powerful and flexible. For example, one custom search engine I created for myself has about 60 third-party websites to search for books. Some of the URLs have path wildcards like example.com/store/product/*. The CSE has result refinements for audiobooks, ebooks, physical books, and technical-style books, all either with or without DRM. The refinements let me add specific URLs already in the engine and rewrite the query with extra keywords (e.g. audiobook, DRM-Free). I tried to create something similar with Kagi Lens but it’s way too limited in its current implementation.