Unity fix for positioning newly created objects in hierarchy below selected object, not at the end of the hierarchy

CreateGameObjectHierarchyPositionFix.cs

/*
 * Copyright 2022 Marcin Swiderski
 * 
 * The MIT Licence (MIT)
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

using UnityEditor;
using UnityEngine;

public static class CreateGameObjectHierarchyPositionFix
{
    private static GameObject _lastActiveGameObject;

    [InitializeOnLoadMethod]
    private static void InitializeOnLoad()
    { 
        Selection.selectionChanged += OnSelectionChanged;
        ObjectChangeEvents.changesPublished += OnObjectChange;
    }
    
    private static void OnSelectionChanged()
    {
        _lastActiveGameObject = Selection.activeGameObject;
    }

    private static void OnObjectChange(ref ObjectChangeEventStream stream)
    {
        for (int eventIdx = 0; eventIdx < stream.length; ++eventIdx) {
            
            if (stream.GetEventType(eventIdx) == ObjectChangeKind.CreateGameObjectHierarchy) {
                stream.GetCreateGameObjectHierarchyEvent(eventIdx, out CreateGameObjectHierarchyEventArgs eventArgs);

                GameObject gameObject = EditorUtility.InstanceIDToObject(eventArgs.instanceId) as GameObject;
                if (gameObject) {
                    if (_lastActiveGameObject != null && gameObject.transform.parent == _lastActiveGameObject.transform.parent) {
                        gameObject.transform.SetSiblingIndex(_lastActiveGameObject.transform.GetSiblingIndex() + 1);
                    }
                }
            }
        }
    }
}

Just add this to editor scripts in your project and you're set :)