Unity Edtor-time Prefab Instantiator For Context Menu

Instantiator.cs

using UnityEditor;
using UnityEngine;

internal class Instantiator : ScriptableObject
{
    private static Instantiator _instance;
    private static Instantiator Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = CreateInstance<Instantiator>();
            }

            return _instance;
        }
    }

    [SerializeField] private GameObject _prefab;

    [MenuItem("GameObject/Foo/Bar", false, 12)]
    private static void Instantiate()
    {
        Selection.activeObject = PrefabUtility.InstantiatePrefab(Instance._prefab);
    }

    [MenuItem("GameObject/Foo/Bar", true, 12)]
    private static bool ValidateInstantiate()
    {
        var go = Instance._prefab;
        return go != null && PrefabUtility.IsPartOfPrefabAsset(go);
    }
}