Arguably that's what BI tools like Tableau and Looker do. Or advanced uses of Excel, which an LLM can help with. The user has data and wants to slice it up and see it in a specific way and have some knobs to play with it to figure out answers to questions as a data scientist.

I've been pondering having some kind of environment that the language model can just modify the application in real time while it is running.

I asked chatgpt and it said hot reloading in a browser, but thats not what i'm talking about. I'm meaning realtime high performance desktop applications that the user can prompt to change the app in realtime while it is running.

The closest thing i saw to this was something called VibeOS, but thats a whole operating system.