Although you can go to https://jsoncanvas.org/ itself and see an example rendering, you cannot see the exact data that created it - I think, although you can sort of guess since the element names are stuff like node.

I sort of doubt this is the best data structure for representing this kind of thing. Maybe I'm wrong though but I would think I would go for something like https://github.com/jsongraph/json-graph-specification which strikes me as closer to graphml which I have some experience with, and maybe give it ability to embed videos etc. (which for all I know someone already has)

This is all an initial feeling though, like hmm, no I think it's wrong, and maybe I am just not seeing why this would be better than another solution.

An "infinite" canvas without some notion of recursion such as viewports feels incomplete.