Creating PolygonCollider2D from points and offset points

Hi everyone. I'm trying to create custom editor extension, and I've stumbled upon problem. Is there a way to create a polygon collider with additional offset points, from already existing sets of points? In a way, that path didn't go the first point, but to offset point instead?

I've got points, and offset points. How to sort them in a proper way? (see picture)

Adding offset points to points array and assigning it creates a total mess. And there's seems to be no proper documentation on how points array sorted. (Or I failed to find any:P)

Any ideas would be appreciated.