[eternityforest]

We already have a good way to do visual diffs: Just store the visual code as text and use Git.

Anything else breaks the ability to use Git, or requires adding plugins which you might have to compile yourself or something, and I'm a big fan of just using Git and having VCS be a solved problem.

If this then that rules map nicely to LISP-like expressions in JSON or YAML.

Freely positionable elements are a pretty bad idea for a lot of things. They make extra noise in the diffs and can't be automatically formatted in a fully satisfying way, short of making an AI for it, plus they can't be edited easily on a mobile device, and they can easily become a literal picture of some spaghetti.