How configure grid graph with multiple level floor

hi there, i am trying to make grid graph for a multiple level floor, but i dont know how and dont find help in the documentation, please i need solve this, under a bridge or a upper level the grid doesnt work.

i just whatch its a pro feature, http://arongranberg.com/astar/docs/class_pathfinding_1_1_layer_grid_graph.php#details

Also the Recast graph (pro) is very good for multilayered environments.