シーンをメニューから開く。メニューに表示するシーンは自動で作成される。 https://github.com/masa795/OpenSceneFromMenuCreator

InitOnLoad.cs

using UnityEngine;
using UnityEditor;


namespace Nlib.Editor.Util
{
  [InitializeOnLoad]
	public class InitOnLoad
	{

		static int couner = 0;

		static InitOnLoad()
		{
			++couner;
			EditorApplication.playmodeStateChanged += ChangedPlaymodeState;
			EditorApplication.update += Update;


			//Log(couner + " InitOnLoad!");
		}


		public static bool IsClickedPlayButton()
		{
			return EditorPrefs.GetBool("editor_InitOnLoad", false);
		}



		static void ChangedPlaymodeState()
		{
			++couner;
			EditorPrefs.SetBool("editor_InitOnLoad", EditorApplication.isPlayingOrWillChangePlaymode);

			//Log(couner + " State Changed!");
		}


		static void Update()
		{
			++couner;
			//Log(couner + " Update!");
			EditorApplication.update -= Update;
		}


		static void Log(string called)
		{
			Debug.Log(called
					+ " \n Application.isPlaying=" + Application.isPlaying
					+ " \n EditorApplication.isPlaying=" + EditorApplication.isPlaying
					+ " \n Application.isCompiling=" + EditorApplication.isCompiling
					+ " \n Application.isPaused=" + EditorApplication.isPaused
					+ " \n EditorApplication.isPlayingOrWillChangePlaymode=" + EditorApplication.isPlayingOrWillChangePlaymode
					+ " \n editor_InitOnLoad=" + EditorPrefs.GetBool("editor_InitOnLoad", false)
					+ " \n Time.timeSinceLevelLoad=" + Time.timeSinceLevelLoad
					+ " \n EditorApplication.timeSinceStartup=" + EditorApplication.timeSinceStartup
					);

		}

	}
}

OpenSceneFromMenuCreator.cs

using UnityEngine;
using UnityEditor;
using System.Linq;
using System.Collections.Generic;
using System;
using System.IO;
using Nlib.Editor.Util;


namespace MenuCreator
{
  /// <summary>
	/// メニューにシーンを開くクラスを自動生成する
	/// </summary>
	[InitializeOnLoad]
	public class OpenSceneFromMenuCreator : Editor
	{

		#region 設定
		/// <summary>シーンを開くスクリプトファイル保存場所 </summary>
		public const string SAVE_DIR = "Editor/OpenMyScenes";
		/// <summary>シーンを開くスクリプトファイル名 </summary>
		public const string SAVE_FILE_NAME = "OpenSceneFromMenu.cs";

		/// <summary>追加するメニュー場所 </summary>
		public const string ADD_MENU_PATH = "nLib/MyScenes/";
		/// <summary>hash </summary>
		private const string SCENENAME_HASH_KEY = "OpenSceneFromMenuCreator_Hash";

		/// <summary>
		/// 除外するパス
		/// 例）
		///		"Assets/NGUI/Examples/Scenes/"
		/// </summary>
		static string[] m_ignorePath = { "Assets/NGUI/Examples/Scenes/" };


		/// <summary>
		/// 対象にしたいパスを指定する
		/// 指定したフォルダ内のみを対象にする
		/// 例）
		///		"Assets/Scenes/"
		/// </summary>
		static string[] m_targetPath = {  };

		#endregion 設定


		/// <summary>
		/// 自動起動
		/// </summary>
		static OpenSceneFromMenuCreator()
		{
			if (EditorApplication.isPlaying || Application.isPlaying)
				return;
			if (InitOnLoad.IsClickedPlayButton() )
				return;

			BuildOpenSceneFromMenu(false);
		}




		[MenuItem(ADD_MENU_PATH + "メニューからシーンを開く【再作成】", false, 20)]
		public static void _OpenSceneFromMenuCreator()
		{
			if (EditorApplication.isPlaying || Application.isPlaying)
				return;
			if (InitOnLoad.IsClickedPlayButton())
				return;
			BuildOpenSceneFromMenu(true);
		}




		#region 書込

		static void BuildOpenSceneFromMenu(bool isRefresh)
		{

			if (!File.Exists(GetSaveFileFullPath()))
			{
				Directory.CreateDirectory(Application.dataPath + "/" + SAVE_DIR);
				System.IO.File.WriteAllText(GetSaveFileFullPath(), "");
			}


			System.Text.StringBuilder builder = new System.Text.StringBuilder();

			builder = WriteSceneManagerClass(builder);
			if (builder == null)
			{
				Debug.Log("No Scene... ");
				return;
			}

			string text = builder.ToString().Replace(",}", "}");
			string assetPath = GetSaveFileFullPath();

			if (ScriptCreatorUtil.CreateFile(assetPath, text, SCENENAME_HASH_KEY, isRefresh))
			{
				Debug.Log("OpenSceneFromMenuCreator　Created " + SAVE_FILE_NAME);
			}


		}


		/// <summary>
		/// メニューからシーンを開く機能のスクリプトを生成する
		/// </summary>
		/// <param name="builder"></param>
		/// <returns></returns>
		static System.Text.StringBuilder WriteSceneManagerClass(System.Text.StringBuilder builder)
		{
			List<string> sceneList = GetCreateSceneList();
			if (sceneList.Count == 0) return null;
			
			builder.AppendLine("using UnityEngine;");
			builder.AppendLine("using UnityEditor;");
			builder.AppendLine("");
			builder.AppendLine("");
			builder.AppendLine("namespace MenuCreator {");

			builder.AppendLine("/// <summary>");
			builder.AppendLine("/// Do not directly edit");
			builder.AppendLine("/// This script is automatic create.");
			builder.AppendLine("/// </summary>");
			builder.AppendLine("public class OpenSceneFromMenu  : Editor ");
			builder.AppendLine("{");

			
			WriteSceneMenue(builder, sceneList);


			builder.AppendLine("}");
			builder.AppendLine("}");
			return builder;
		}



		/// <summary>
		/// メニュー　アイテムを作成する
		/// </summary>
		/// <param name="builder"></param>
		/// <param name="sceneList"></param>
		static void WriteSceneMenue(System.Text.StringBuilder builder, List<string> sceneList)
		{
			sceneList.ToList().ForEach(sceneName =>
			{
				string replaceName = ReplaceForMenuName(sceneName);
				string replaceFunctionName = ReplaceForFunctionName(sceneName);

				builder.AppendLine("");
				builder.Append("\t").AppendLine("[MenuItem(\"" + ADD_MENU_PATH + replaceName + " \", false, 50)]");
				builder.Append("\t").AppendLine("public static void Open" + replaceFunctionName + "(){");

				builder.Append("\t").Append("\t").AppendLine("if (EditorApplication.SaveCurrentSceneIfUserWantsTo() == true){");
				builder.Append("\t").Append("\t").Append("\t").AppendLine("EditorApplication.OpenScene(\"" + sceneName + "\");");
				builder.Append("\t").Append("\t").AppendLine("}");

				builder.Append("\t").AppendLine("}");
				builder.AppendLine("");
			});
		}

		#endregion 書込




		#region 対象シーン
		/// <summary>
		/// 生成するためのシーンリストを取得する
		/// </summary>
		/// <returns></returns>
		private static List<string> GetCreateSceneList()
		{
			List<string> sceneList = new List<string>();

			string[] allAssets = AssetDatabase.GetAllAssetPaths();
			foreach (string assetPath in allAssets)
			{
				if (Path.GetExtension(assetPath).ToLower() == ".unity")
				{
					if (!IsTargetItem(assetPath))
						continue;
					else if (IsIgnoreItem(assetPath))
						continue;

					//Debug.Log("assetPath=" + assetPath + "    GetExtension=" + Path.GetExtension(assetPath));
					sceneList.Add(assetPath);
				}
			}
			return sceneList;
		}


		/// <summary>
		/// 除外するシーンか
		/// </summary>
		/// <param name="assetPath"></param>
		/// <returns></returns>
		private static bool IsIgnoreItem(string assetPath)
		{
			if (m_ignorePath.Length == 0) return false;
			foreach (string path in m_ignorePath)
			{
				if (assetPath.Contains(path))
				{
					return true;
				}
			}
			return false;
		}


		/// <summary>
		/// 指定されたパスか
		/// </summary>
		/// <param name="assetPath"></param>
		/// <returns></returns>
		private static bool IsTargetItem(string assetPath)
		{
			if (m_targetPath.Length == 0) return true;

			foreach (string path in m_targetPath)
			{
				if (assetPath.Contains(path))
				{
					return true;
				}

			}
			return false;
		}
		#endregion 対象シーン


		#region util


		/// <summary>
		/// 関数名に使えない文字を置換する
		/// </summary>
		/// <param name="name"></param>
		/// <returns></returns>
		static string ReplaceForFunctionName(string name)
		{
			string[] invalidChar = new string[] { " ", "!", "\"", "#", "$", "%", "&", "\'", "(", ")", "-", "=", "^", "~", "\", "|", "[", "{", "@", "`", "]", "}", ":", "*", ";", "+", "/", "?", ".", ">", ",", "<" };
			invalidChar.ToList().ForEach(s => name = name.Replace(s, string.Empty));
			return name;
		}


		/// <summary>
		/// メニューに表示できない文字を置換
		/// </summary>
		/// <param name="name"></param>
		/// <returns></returns>
		static string ReplaceForMenuName(string name)
		{
			string[] invalidChar = new string[] { "/" };
			invalidChar.ToList().ForEach(s => name = name.Replace(s, "|"));
			invalidChar = new string[] { "&" };
			invalidChar.ToList().ForEach(s => name = name.Replace(s, ""));
			return name;
		}





		static string GetSaveFilePath()
		{
			return "Assets/" + SAVE_DIR + "/" + SAVE_FILE_NAME;
		}

		static string GetSaveFileFullPath()
		{
			return Application.dataPath + "/" + SAVE_DIR + "/" + SAVE_FILE_NAME;
		}



		static List<EditorBuildSettingsScene> GetEnableScenes()
		{
			return EditorBuildSettings.scenes.Where(scene => scene.enabled).ToList();
		}

		static string currentFolderPath
		{
			get
			{
				string currentFilePath = new System.Diagnostics.StackTrace(true).GetFrame(0).GetFileName();
				string currentFolderPath = currentFilePath.Substring(0, currentFilePath.LastIndexOf(Path.DirectorySeparatorChar) + 1).Replace(Path.DirectorySeparatorChar, '/');
				return "Assets" + currentFolderPath.Replace(Application.dataPath, string.Empty);
			}
		}
		#endregion util

	}
}

ScriptCreatorUtil.cs

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


namespace Nlib.Editor.Util
{
  /// <summary>
	/// スクリプト自動生成util
	/// </summary>
	public class ScriptCreatorUtil
	{

		/// <summary>
		/// ファイルを作成する
		/// </summary>
		/// <param name="assetPath"></param>
		/// <param name="output"></param>
		/// <param name="prefsHashKey"></param>
		/// <param name="isRefresh"></param>
		/// <returns></returns>
		public static bool CreateFile(string assetPath, string output, string prefsHashKey, bool isRefresh)
		{
			if (!isRefresh)
			{
				if (File.Exists(assetPath) && EditorPrefs.GetInt(prefsHashKey) == output.GetHashCode())
					return false;

				if (EditorPrefs.GetInt(prefsHashKey) == output.GetHashCode())
					return false;
			}

			if (string.IsNullOrEmpty(output))
			{
				return false;
			}
			else
			{
				if (System.IO.File.ReadAllText(assetPath) == output)
				{
					EditorPrefs.SetInt(prefsHashKey, output.GetHashCode());
					return false;
				}
			}


			System.IO.File.WriteAllText(assetPath, output);
			EditorPrefs.SetInt(prefsHashKey, output.GetHashCode());


			AssetDatabase.SaveAssets();
			AssetDatabase.Refresh();

			//AssetPostprocessUTF8Encode.ConvertUtf8WithBom(assetPath);

			return true;
		}


		public static void WriteNormalMember<T>(System.Text.StringBuilder builder, T sourceClass, string[] ignoreMembers)
		{
			System.Reflection.FieldInfo[] fields = sourceClass.GetType().GetFields();
			foreach (System.Reflection.FieldInfo field in fields)
			{
				if (IsIgnoreMember(ignoreMembers, field.Name)) continue;

				WriteMember(builder, sourceClass, field);

			}
		}




		public static void WriteMember<T>(System.Text.StringBuilder builder, T sourceClass, System.Reflection.FieldInfo field)
		{
			builder.AppendLine("");
			if (field.GetValue(sourceClass) is string)
			{
				WriteStringMember(builder, field.Name, (string)field.GetValue(sourceClass));
			}
			else if (field.GetValue(sourceClass) is Int32)
			{
				WriteIntMember(builder, field.Name, (int)field.GetValue(sourceClass));
			}
			else if (field.GetValue(sourceClass) is bool)
			{

				WriteBoolMember(builder, field.Name, (bool)field.GetValue(sourceClass));
			}
		}



		static bool IsIgnoreMember(string[] ignoreMembers, string memberName)
		{
			if (ignoreMembers.Length == 0) return false;
			foreach (string name in ignoreMembers)
				if (name == memberName) return true;
			return false;
		}



		#region write string
		public static void WriteStringMember(System.Text.StringBuilder builder, string memberName, string value)
		{
			builder.AppendLine("");
			WriteMemberDocSummaryString(builder, value);
			builder.Append("\t").AppendFormat(@"public const string {0} = ""{1}"";", memberName, value).AppendLine();
		}
		static void WriteMemberDocSummaryString(System.Text.StringBuilder builder, string value)
		{
			builder.Append("\t").AppendLine("/// <summary>");
			builder.Append("\t").AppendFormat("/// return \"{0}\"", value).AppendLine();
			builder.Append("\t").AppendLine("/// </summary>");
		}
		#endregion write string




		#region write int
		public static void WriteIntMember(System.Text.StringBuilder builder, string memberName, int value)
		{
			builder.AppendLine("");
			WriteMemberDocSummaryInt(builder, value.ToString());
			builder.Append("\t").AppendFormat(@"public const int {0} = {1};", memberName, value).AppendLine();
		}
		static void WriteMemberDocSummaryInt(System.Text.StringBuilder builder, string value)
		{
			builder.Append("\t").AppendLine("/// <summary>");
			builder.Append("\t").AppendFormat("/// return {0}", value).AppendLine();
			builder.Append("\t").AppendLine("/// </summary>");
		}
		#endregion write int


		#region write bool
		public static void WriteBoolMember(System.Text.StringBuilder builder, string memberName, bool value)
		{
			builder.AppendLine("");
			string strVal = (value) ? "true" : "false";
			WriteMemberDocSummaryInt(builder, strVal);
			builder.Append("\t").AppendFormat(@"public const bool {0} = {1};", memberName, strVal).AppendLine();
		}
		static void WriteMemberDocSummaryBool(System.Text.StringBuilder builder, string value)
		{
			builder.Append("\t").AppendLine("/// <summary>");
			builder.Append("\t").AppendFormat("/// return {0}", value).AppendLine();
			builder.Append("\t").AppendLine("/// </summary>");
		}
		#endregion write bool



	}
}