Build boundaries around levels or zones that block the player and then generate a mesh to go along with it so that your navmesh can respect those boundaries as well.
I've used some boundary tools in the past, and none of them met my expectations. I wanted better, so I built better.
Notable Features
Add nodes to your scene that turn into a boundary with a few simple clicks
Makes sure your navmesh and the AI that uses it respects the same boundaries your player does
See the boundary being created in real-time without having to bake it
Simple, lightweight, easy to use