I think that to be most useful the dynamic properties might not be just things that you can update in a fig.update_layout call but would directly change some of the arguments of the original px.scatter (or whatever) function. Like log_x, log_y, size etc. In fact we could do better than just updating the graph it shows and also update the code snippet on the fly too.
Maybe it would be a bit like a very simplified version of https://chart-studio.plotly.com/ but for plotly express graphs only (and without data upload I guess). Ideally there’d be some way of automatically parsing plotly express and figuring out from that how to make a form to apply those options like a dropdown or checkbox etc. Unfortunately I don’t think there’s a schema for plotly express? And the source code doesn’t have arguments type annotated so it would probably need to use docstrings which isn’t so good. So probably this isn’t feasible for now, and instead we’d need to manually pick 5-10 “most commonly modified” argument for each chart.