LoadSceneWindow.cs

using System.Linq;
using UnityEngine;
using UnityEditor;
using UnityEngine.SceneManagement;
using UnityEditor.SceneManagement;

public class LoadSceneWindow : EditorWindow
{
	[MenuItem ("Custom/Scene")]
	static public void Open ()
	{
		LoadSceneWindow window = GetWindow<LoadSceneWindow> (false);
		window.minSize = new Vector2 (200.0f, 22.5f);
		window.maxSize = new Vector2 (400.0f, 22.5f);
	}


	SceneAsset[] m_Scenes;
	SceneAsset m_CurrentScene;
	bool m_WasInitialized = false;


	void Initialize ()
	{
		var sceneGUIDs = AssetDatabase.FindAssets ("t:scene");
		m_Scenes = sceneGUIDs.Select (arg => AssetDatabase.LoadAssetAtPath<SceneAsset> (AssetDatabase.GUIDToAssetPath (arg))).ToArray ();

		m_CurrentScene = m_Scenes.Where (arg => arg.name.Equals (SceneManager.GetActiveScene ().name)).FirstOrDefault ();

		m_WasInitialized = true;
	}

	void OnGUI ()
	{
		if (!m_WasInitialized) {
			Initialize ();
			return;
		}
		EditorGUI.BeginDisabledGroup (EditorApplication.isPlayingOrWillChangePlaymode);
		EditorGUILayout.BeginHorizontal ();

		var prevIdx = ArrayUtility.IndexOf <SceneAsset> (m_Scenes, m_CurrentScene);
		var nextIdx = EditorGUILayout.Popup (prevIdx, m_Scenes.Select (arg => arg.name).ToArray ());
		if (prevIdx != nextIdx) {
			if (EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo ()) {
				m_CurrentScene = m_Scenes [nextIdx];
				EditorSceneManager.OpenScene (AssetDatabase.GetAssetPath (m_CurrentScene));
			}
		}

		if (GUILayout.Button ("Select")) {
			Selection.activeObject = m_CurrentScene;
		}
		EditorGUILayout.EndHorizontal ();
		EditorGUI.EndDisabledGroup ();
	}

	void Update ()
	{
		if (!m_WasInitialized) {
			Initialize ();
			return;
		}

		if (m_CurrentScene != null && !m_CurrentScene.name.Equals (SceneManager.GetActiveScene ().name)) {
			m_CurrentScene = AssetDatabase.LoadAssetAtPath<SceneAsset> (SceneManager.GetActiveScene ().path);
			Repaint ();
		}
	}

	void OnEnable ()
	{
		Initialize ();
	}
}