The original "Block Editor" (that Jupyter modeled itself after) is the one that's now called "Quanta", and has been around for decades in various forms and incantations:
I meant the "block editor" aspect, like how individual chunks of text and images can be independently selected and moved around or even shared with their own URL.
I've long believed some system like that could and should some day replace even HTML and the web, and that it'll only happen if the Semantic Web ever takes off in a big way where chunks of stuff are "typed" (like a Type-Safe Web). Even Tim Berners Lee has been dreaming of this for decades, but the world is still stuck in HTML-land for the foreseeable future.
Yes, but it's closer to Sage (browser and Python based).
I don't know what quantadev is thinking of, but Quanta seems totally different and not a programming notebook at all. Its README also claims "Quanta is a new kind of platform with a new kind of architecture", while quantadev claims it "has been around for decades".
https://github.com/Clay-Ferguson/quantizr
I'm thinking that Jupyter might still not be "Tree Based" but that would be a heck of a leap in capability if they "fix" that.