Multiple Navmesh Bakes

Hello, guys I have a question. Is the Navmesh bake additive? I mean, if I bake a navmesh, when I bake again, the previous baked data will be added? Or overwritten?

Overwritten

Ok Thank you! Is there a way to achieve that “addition”? I think that maybe I can use the Navmesh Surface component, but it doesn’t generate offmesh links, does it?