Instead of demo do you mean NavMeshAgent? The demo isn't anything special and as long as you are using a NavMeshAgent you can use any of the built in tasks. I mentioned above but there's also an A* integration. You will need to take the approach of implementing a new navigation system.
The built-in demo scene uses a NavMeshAgent but there are integrations with the A* Pathfinding Project and PolyNav for the Movement Pack. Behavior Designer itself doesn't use the NavMeshAgent at all.
Have you watched the set of behavior tree basics videos? You can follow the setup from those videos and expand from there:
You can use conditional aborts: