Is there any way to edit comments? xD
My solution below requires LinQ, null propagation

Here's an edited version that works with polygoncollider2d. It seems that PolygonCollider2DEditor has to be set to edit mode in the next "frame" rather than when its exit mode ended.

[InitializeOnLoadMethod]
public static void InitLoad()
{
EditMode.onEditModeEndDelegate -= Collider2DEditModeFixer;
EditMode.onEditModeEndDelegate += Collider2DEditModeFixer;
}

static void Collider2DEditModeFixer(Editor editor)
{
if (EditMode.editMode == EditMode.SceneViewEditMode.Collider || EditMode.IsOwner(editor)) return;

var sel = Selection.activeGameObject;
var cols = sel?.GetComponents<Collider2D>();
if (cols == null || cols.Length == 0) return;

var t = editor.target as Collider2D;
if (t != null && (cols?.Contains(t) ?? false))
{
EditorApplication.delayCall += () => EditMode.ChangeEditMode(EditMode.SceneViewEditMode.Collider, t.bounds, editor);
}
}

I created an automated fix for this. Sometimes i have multiple colliders in the same object so choosing just the first editor to edit won't work.
The only downside is that if you want to exit the collider edit mode you have to select another object.

[InitializeOnLoadMethod]
public static void InitLoad()
{
EditMode.onEditModeEndDelegate -= Collider2DEditModeFixer;
EditMode.onEditModeEndDelegate += Collider2DEditModeFixer;
}

static void Collider2DEditModeFixer(Editor editor)
{
var sel = Selection.activeGameObject;
var cols = sel?.GetComponents<Collider2D>();

var t = editor.target as Collider2D;
if (t != null && cols.Contains(t))
{
EditMode.ChangeEditMode(EditMode.SceneViewEditMode.Collider, t.bounds, editor);
}
}

I guess you do know the workaround, but anyways: editing an GameObject's collider in the scene, will not quit "Edit Collider" mode.

Also, I composed a plugin/Script for working in Prefab Editor, (works by hitting Shift+E on every change... xD .. better than nothing!), with some code I found in stack-overflow :

----------------------------------
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

public class MenuItems
{
[MenuItem("BugFixes/Edit Collider Mode #_e")] // This is Shift + e
private static void EditCollider()
{
var sel = Selection.activeGameObject; if(!sel) return;
var col = sel.GetComponent<Collider2D>(); if (!col) return;

if (UnityEditorInternal.EditMode.editMode == UnityEditorInternal.EditMode.SceneViewEditMode.Collider)
UnityEditorInternal.EditMode.ChangeEditMode(UnityEditorInternal.EditMode.SceneViewEditMode.None, new Bounds(), null);
else
{
System.Type colliderEditorBase = System.Type.GetType("UnityEditor.ColliderEditorBase,UnityEditor.dll");
Editor[] colliderEditors = Resources.FindObjectsOfTypeAll(colliderEditorBase) as Editor[];

if (colliderEditors == null || colliderEditors.Length <= 0) return;

UnityEditorInternal.EditMode.ChangeEditMode(UnityEditorInternal.EditMode.SceneViewEditMode.Collider, col.bounds, colliderEditors[0]);
}
Debug.Log("EditMode: " + UnityEditorInternal.EditMode.editMode);
}
}
----------------------------------

The link from which I found most of the code (ready) is this one:
https://forum.unity.com/threads/creating-a-hotkey-to-get-into-edit-collider-mode.474706/
So, most credits go to him.

P.S.: "Place in a folder called 'Editor' in order to work as a plugin", that's what I did, and it worked.