I wrote 2 tutorials this month about implementing a behavior tree from scratch (here and here), which content was based on this library. Together with the core classes and nodes, I also released an online and visual editor, where you can design your behavior tree with custom nodes and export it to JSON format.
Unfortunately, I couldn’t release the visual debugger together (I will travel next week, so I preferred to release what I had right now), but for sure, this is the priority for the next versions.
Take a look in this project on Github: https://github.com/renatopp/behavior3js
I recommend you to also take a look at the user guide, so you can have an idea of how this works: https://github.com/renatopp/behavior3js/wiki