.@jrus based on this response from @mbostock I suspect load/save notebook api is not in the current roadmap:
One could probably do it via raw XHR to observable api, but I don’t know if I would want to go there. would require some time to reverse engineer those calls. not impossible, but would be time consuming and hacky AF.
I’ll wait for the official public API and open source of observable for private hosting, etc. others have requested on this forum similar to how one can do with Jupyter notebooks today.