Is there a list of walkable?

In my game, I would like to highlight all the walkable tiles on the map when the player clicks on a unit so he can see where that unit is allowed to move.
So after scanning the grid graph, is there a way to get back a list of all walkable tiles of the grid?

Yes. You can use and then only show the nodes for which node.Walkable is true.

See Accessing graph data - A* Pathfinding Project

Thank you. That worked.