Created by Rob VR Bits and is 100% based on the work of a person from the internet. But I don't want to mention the name because the person wants to get people as patreons to give him money for his work. And I don't want to undermine that. Everything I publish here, the person has already published himself via Youtube and I hope that's OK. If you want to know who it is, just ask me.
Here is a simple template with a running GraphView example. The example contains 4 concrete type of nodes (Debug, Repeat, Sequence, Wait) that derrive from 3 types of basic nodes (Action, Decorator, Composite). The example also contains a custom graph editor window that allows you to create and edit graphs. The whole Graph is persisted as ScriptableObjects asset in the project.
All you need is to put the BehaviourTreeRunner on an MonoBehaviour and add a SceneFlowConfiguration ScriptableObject to it. The SceneFlowConfiguration can be created via the CreateAssetMenu under the folder "vrbits".