This is a paid asset, but now you can download Easy Collider Editor Free.
Detail this asset from Unity Store: Original Link
Easy Collider Editor v6.0 (Latest version)
Easy Collider Editor v5.6
Easy Collider Editor v4.1
Easy Collider Editor v3.0.1
Easy Collider Editor v2.5
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Easy Collider Editor is designed to make creating and positioning box, sphere, capsule, and convex mesh colliders as easy as possible.
This tool lets you quickly and easily add multiple colliders on gameobjects using simple and easy to use vertex selection tools. No more painfully adding, moving, and resizing colliders. A helpful preview option is now available that makes the process even easier.
Simply select vertices or points on the mesh, click a button, and a box, capsule, sphere, rotated box, rotated capsule, or convex mesh collider will be generated.
Selection of vertices is even easier with the newly added box selection, ring selection, point selection, and grow selection tools.
The latest update also makes it easy to automatically generate colliders for a skinned mesh.