Marking area on Terrain

I want my object move to clicked point of terrain.Is there a way I can mark areas on terrain with a brush (like I do with textures), where it can go and it cannot.It would help with path-finding as well as with finding out if that point is accessible on not.at the point I only t$$anonymous$$nk of placing coliders at accessible points, but I don't t$$anonymous$$nk it will work in path-finding.