Can you publish a collection item without a page associated with it?

I have a large collection of items, some of which I want to have their own page as usual, but some I only want to appear in the listing page without any associated endpoint. This is easy to do from a link perspective using conditional visibility, but how do I prevent the pages from being created so they don’t appear in search? Alt is there a way to programmatically add a no index / no robots tag based on the CMS data?

No. But you can manually handle this via your robots.txt file. If a CMS item is published it is visible if you have the URL.