Something like this:
Image

Similar to what is possible with shapes when editable=True is set in the config: https://github.com/plotly/plotly.js/blob/master/src/plot_api/plot_config.js#L47

Changing the position of the point (or bar section) should:

• modify the underlying traces
• trigger an event like restyle or relayout
• be restricted based on the current state of the graph. In the example of the screenshot, it should only be possible that the bar region is moved to "China" or "Canada" and their respective x positions, since those are the available values. Similarly, the y position would be determined by the current "height" of the bar the region is moved to.