This is a paid asset, but now you can download Easy Wall Collider Free.
Detail this asset from Unity Store: Original Link
Easy Wall Collider v1.3 (Latest version)
Block out your level colliders in a matter of seconds!
Draw a polygon around your level, and this script automatically generates box and capsule colliders matching the shape.
No more tedious scaling and rotating of box colliders.
– Live editing of the shape
– Add and delete inbetween points on the fly
– Rounded corners, so players don`t get stuck behind them
– Make closed loops
– Super good performance by using Unity’s box and capsule colliders. (0 mesh colliders involved)
– Enabling and disabling renderers in 1 click, for navmesh generation.
– Editing the collider while playing (only intended as editor tool)