The new JSON features are very powerful and will be useful, but their syntax can be a little tricky. It reminds me of some struggles I've had working with KM dictionaries since those were introduced.
One of the nice things about KM variables is that I can see a complete list of them in the Preferences pane. When something isn't working the way I expect it to, I often keep an eye on the relevant variable in that pane to see when and how they change.
It would be a great time-saver if there were an equivalent way for me to see what dictionaries and JSON objects KM is managing, and what their content is.
Agreed. That is one of the main reasons I almost never use KM Dictionaries.
IMO, it would be best to move ALL of the data-related stuff out of KM Preferences (since the data has nothing to do with Preferences), and into separate, resizable, windows, listed under the Window menu.
Yes, it would be. But there is a reason there is support for dictionaries and JSON and not a UI for it, and that is that it will be a lot of work to do the latter. It may eventually come, but it is a lot of work (there are entire programs that handle just this sort of thing, and so having it as one small feature of Keyboard Maestro gives you an idea of the magnitude of it).
You can, of course, use the tools available to create your own display of dictionaries and JSON variables. All the tools should already be there to display or edit them in a Custom HTML window.
Perhaps you could just start off with something simple, like a window that in the left panel displays a list of Dictionaries, and in the right panel the pretty form of output as a JSON string.