This is a product I REALLY want. Since I want to be able to diagram entire complex systems without always seeing 10,000 boxes on screen. You could start a presentation at 35,000 feet, showing the entire rough structure, then zoom into different regions where more detail will appear (infinitely)
Nestable feels more like excalidraw, with a folder/file structure?
Maybe on a smaller scale, it would be manageable though. I remember seeing some presentations that use Prezi and that has the ability to nest text at different zoom levels, and the transitions between slides worked pretty well and you did still have a sense of place, but the presenters didn't have tons of content all over like in the youtube link. I wish I had a link handy for the Prezi presentation I saw online because some of them were structured like your description about different zoom levels, like a fractal.
I was surprised at how easy it was to learn Graffiti and how quick it was to use it. Not as fast as typing, but better than hunting and pecking on an on-screen keyboard with a stylus. I didn't like how the stylus felt on the screen when you wrote so I cut a little piece of a post-it note and put on the area where you'd do the Graffiti strokes.
I don't remember exactly how it worked, but I was able to save some web articles onto the device. When I was on a lunch break, I'd read through the articles on that little thing. It truly felt like living in the future.