It definitely was! That’s why we prioritized it 
As you can see from the open source GitHub issue that I posted above (Persistent and Multiple Clicking and Unclicking Behaviour · Issue #1852 · plotly/plotly.js · GitHub) this was actually solved via the selectedpoints property through this monumental PR: 1852 persistent click via select points by rmoestl · Pull Request #2944 · plotly/plotly.js · GitHub. I don’t think any Dash-specific examples have made it through to the docs yet, but you may be able to figure it out via the plotly.js examples included in that PR.
Always appreciate the feedback!