If it weren't for the "interactive" part, I would suggest to take a look at this SO question and answers.
Since you are mentioning commercial libraries, I assume that this is in a commercial scenario, and thus I believe this interactive flow-chart demo is pretty much exactly what you are looking for. Maybe also this BPMN editing demo.
The demos are using the commercial yFiles for HTML Javascript/HTML5 diagramming library. The library provides (among other features) editing capabilities for flow-chart-like and BPMN diagrams, has robust support for (optionally hierarchical, two-dimensional) swim lanes and of course adding custom data and custom interaction logic is easily supported. The most advanced feature though is the ability to automatically arrange the elements on the screen according to the flow-chart logic:

Disclaimer: I work for the company that creates this library. I do not represent my employer on SO, though.