レイヤーでシーン内のゲームオブジェクトを検索するエディタスクリプトです。

下図のようにレイヤーを指定して、そのレイヤーに属するシーン内のゲームオブジェクトを検索、列挙できます。
下図はEventレイヤーに属するゲームオブジェクトを検索、列挙している例です。
Editorフォルダに入れて使って下さい。

FindSceneObjectsWithLayer.cs

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

public class FindSceneObjectsWithLayer : EditorWindow
{
	public int LayerToSearchFor = 0;

	public bool LimitResultCount = false;
	public int MaxResults = 1;

	public List<GameObject> Results;
	private Vector2 ResultScrollPos;

	void OnGUI()
	{
		EditorGUILayout.BeginVertical();
		{
			EditorGUILayout.LabelField("Options", EditorStyles.boldLabel);
			{
				GUILayout.BeginHorizontal();
				EditorGUILayout.LabelField("Layer : ", GUILayout.MaxWidth(60));
				LayerToSearchFor = EditorGUILayout.LayerField(LayerToSearchFor);
				GUILayout.EndHorizontal();

				if (GUILayout.Button("Find"))
					Find();

				if (LimitResultCount = EditorGUILayout.Foldout(LimitResultCount, "Limit Result Count (Limit:"
						+ (LimitResultCount ? MaxResults.ToString() : "None") + ")"))
					MaxResults = EditorGUILayout.IntField("Result Max:", MaxResults);
			}

			EditorGUILayout.LabelField("Results", EditorStyles.boldLabel);
			{
				if (Results != null)
				{
					EditorGUILayout.LabelField("Scene objects found:", Results.Count.ToString(), EditorStyles.boldLabel);

					ResultScrollPos = EditorGUILayout.BeginScrollView(ResultScrollPos);
					{
						if (LimitResultCount)
						{
							for (int i = 0; i < Mathf.Min(MaxResults, Results.Count); i++)
								EditorGUILayout.ObjectField(Results[i], typeof(GameObject), false);
						}
						else
						{
							foreach (GameObject go in Results)
								EditorGUILayout.ObjectField(go, typeof(GameObject), false);
						}
					}
					EditorGUILayout.EndScrollView();
				}
			}
		}
		EditorGUILayout.EndVertical();
	}

	void Find()
	{
		GameObject[] goArray = FindObjectsOfType(typeof(GameObject)) as GameObject[];
		Results = new List<GameObject>();
		for (int i = 0; i < goArray.Length; i++)
		{
			if (goArray[i].layer == LayerToSearchFor)
			{
				Results.Add(goArray[i]);
			}
		}
	}

	[MenuItem("Tools/Find By Layer...")]
	static void Init()
	{
		FindSceneObjectsWithLayer window = EditorWindow.GetWindow<FindSceneObjectsWithLayer>("Find By Layer");
		window.ShowPopup();
		//window.ShowAuxWindow();
	}
}