Agreed. The way how I see it, it's not a core competency of a notebook though (it's important to keep the medium itself versatile enough), but of an extension. As you mentioned, there are some startups working exactly on this (thus very likely a much better job than a notebook), so it's probably a problem of a missing link (like a nice API for UI extension).

Speaking on behalf of Deepnote, there's no such an API yet, but it's something that I'd definitely like to see and build.