Can you create 2D polygon colliders in a 3D modelling program? (Blender)

I need to create a complex shape that cannot easily be created with the polygon editor. I made this in blender (it is co-planar, so should be able to be a 2D polygon), but can't find a way to use it as a polygon collider. Is there a way to do this?

edit: Is there a polygon renderer? I want to plan out a level with polygons before creating art.

 

I'm not sure why you would need blender to make a 2D collider. What do you need it for? Are you making a 2D game or 3D. I know that doesn't make alot of sense, but, if you're making a 2D game, just make a sprite in Inkscape or Hexels or something and import as a SPRITE/2D GUI texture, and use the polygon collider component. You can manually edit the collider from there. Hope this helps, although I'm not really sure what you're talking about. Also, use pen and paper to plan out your levels. doing it in unity or blender or on a computer isn't really that practical. Go get yourself some level design (graph/grid) paper and start planning. WOLD is a good resource for that sort of LVD stuff.