Pick a Collider2D in Unity Editor SceneView - LisTechBlog
Unity Collider2D Optimization by Alchem
Fixed a glitch with composite colliders - Talk - GameDev.tv
Unity - Manual: Composite Collider 2D
Unity - Manual: Edge Collider 2D
Unity - Manual: Box Collider 2D
GitHub - HawkenKing/Edge-collider2D-to-Polygon-collider-2D: This script will change any edge collider2D to a polygon collider2D, originally written to convert edge colliders in 2DtoolKit