An Unity editor window helper to show gameObjects in scene or project per tag or layer.

SearchTagLayer.cs

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

public class SearchTagLayer : EditorWindow
{
	//Scene/Project
	private string[] _as_sceneProject = new string[2]{"Scene", "Project"};
	private int _i_sceneProjectIndex = 0;

	//Tag/Layer
	private string[] _as_tagLayer = new string[2]{"Tag", "Layer"};
	private int _i_tagLayerIndex = 0;

	//|| TAG ||
	//Genuine tag list
	private string[] _as_tags;
	//Main 2D array [tag][object]
	private GameObject[][] _aaGO_tags;
	//Foldout boolean for each tag
	private bool[] _ab_foldout_tags;
	//Main Scroll
	private Vector2 _V2_scroll_mainTag = Vector2.zero;

	//|| LAYER ||
	//Main 2D array
	public GameObject[][] _aaGO_layers;
	//Foldout boolean for each layer
	private bool[] _ab_foldout_layers;
	//Main scroll
	private Vector2 _V2_scrollVert_layers = Vector2.zero;

	//|| MAIN DIRECTORY ||
	public enum eMainDirectory
	{
		Scene = 0,
		Project = 1,
		Both = 2
		
	}// eMainDirectory

	[MenuItem("Window/Show GameObject Tag-Layer")]
	private static void Init()
	{
		SearchTagLayer _window = GetWindow<SearchTagLayer>();
		_window.title = "Tags/Layers";
		_window.Show();
		
	}// Init
	
	
	private void OnGUI()
	{
		//Pick from Scene or Project ?
		_i_sceneProjectIndex = GUILayout.SelectionGrid(_i_sceneProjectIndex, _as_sceneProject, 2);

		//Pick with Tag or Layers ?
		_i_tagLayerIndex = GUILayout.SelectionGrid(_i_tagLayerIndex, _as_tagLayer, 2);

		switch(_i_tagLayerIndex)
		{
		
		//|| TAG ||
		case 0:
		{
			if(GUILayout.Button("Refresh"))
			{
				//Reset ref
				_aaGO_tags = null;
				_ab_foldout_tags = null;
				_V2_scroll_mainTag = Vector2.zero;

				if(_i_sceneProjectIndex == 0) GetListByTagsFromScene();
				else GetListByTagsFromProject();
			}

			if(_aaGO_tags != null)
			{
				_V2_scroll_mainTag = EditorGUILayout.BeginScrollView(_V2_scroll_mainTag);

				//Show each tags
				for(int i = 0; i < _aaGO_tags.Length; i++)
				{
					if(_aaGO_tags[i] != null)
					{
						_ab_foldout_tags[i] = EditorGUILayout.Foldout(_ab_foldout_tags[i], _as_tags[i] + ":" + _aaGO_tags[i].Length.ToString());
						
						if(_ab_foldout_tags[i])
						{
							EditorGUI.indentLevel++;

							//Show each GameObject
							for(int j = 0; j < _aaGO_tags[i].Length; j++)
							{
								if(_aaGO_tags[i][j] != null)
								{
									EditorGUILayout.BeginHorizontal();

									//Ping ?
									if(GUILayout.Button("?", GUILayout.ExpandWidth(false)))
									{
										EditorGUIUtility.PingObject(_aaGO_tags[i][j]);
									}

									//Select name ?
									if(GUILayout.Button(_aaGO_tags[i][j].transform.name))
									{
										Selection.activeGameObject = _aaGO_tags[i][j];
									}

									EditorGUILayout.EndHorizontal();
								}
								
							}//for()
							
							EditorGUI.indentLevel--;
						}
					}
					
				}//for()

				EditorGUILayout.EndScrollView();
			}

		}break;
		
		//|| LAYER ||
		case 1:
		{
			//Refresh button
			if(GUILayout.Button("Refresh"))
			{
				//Reset ref
				_aaGO_layers = null;
				_ab_foldout_layers = null;
				_V2_scrollVert_layers = Vector2.zero;

				if(_i_sceneProjectIndex == 0)
				{
					GetListByLayersFromScene();
				}
				else
				{
					GetListByLayersFromProject();
				}
			}

			if(_aaGO_layers != null)
			{
				_V2_scrollVert_layers = EditorGUILayout.BeginScrollView(_V2_scrollVert_layers);

				//Show each layers
				for(int i = 0; i < 32; i++)
				{
					//Not Empty ?
					if(_aaGO_layers[i] != null)
					{
						//Foldout ?
						_ab_foldout_layers[i] = EditorGUILayout.Foldout(_ab_foldout_layers[i], i.ToString() + "|" + LayerMask.LayerToName(i) + ":" + _aaGO_layers[i].Length.ToString());
						
						if(_ab_foldout_layers[i])
						{
							EditorGUI.indentLevel++;
							
							//Show each gameObject
							for(int j = 0; j < _aaGO_layers[i].Length; j++)
							{
								//Safety
								if(_aaGO_layers[i][j] != null)
								{
									EditorGUILayout.BeginHorizontal();
									
									//Ping ?
									if(GUILayout.Button("?", GUILayout.ExpandWidth(false)))
									{
										EditorGUIUtility.PingObject(_aaGO_layers[i][j]);
									}
									
									//Select name ?
									if(GUILayout.Button(_aaGO_layers[i][j].transform.name))
									{
										//Select in scene
										Selection.activeGameObject = _aaGO_layers[i][j];
									}
									
									EditorGUILayout.EndHorizontal();
								}

							}//for()
							
							EditorGUI.indentLevel--;
						}
					}

				}//for()

				EditorGUILayout.EndScrollView();
			}

		}break;
		
		default:break;
		
		}//switch(_i_tagLayerIndex)
		
	}// OnGUI


	private void GetListByTagsFromScene()
	{
		//Get genuine tags list
		_as_tags = UnityEditorInternal.InternalEditorUtility.tags;

		//Get all gameobjects from scene
		GameObject[] _aGO_sceneGOs = GetAllGameObjects(eMainDirectory.Scene);

		//Set temp list/array
		List<GameObject>[] _aLGO_sortedList = new List<GameObject>[_as_tags.Length];

		//Setup main 2D array
		_aaGO_tags = new GameObject[_as_tags.Length][];

		//Setup foldout array
		_ab_foldout_tags = new bool[_as_tags.Length];

		//Init every tag'list
		for(int o = 0; o < _aLGO_sortedList.Length; o++)
		{
			_aLGO_sortedList[o] = new List<GameObject>();
			
		}//for()

		//Loop through every gameobjects from scene
		for(int i = 0; i < _aGO_sceneGOs.Length; i++)
		{
			//Get tag'index
			int _i_tagIdx = TagToIndex(_aGO_sceneGOs[i].tag);

			//Not already inside the list ?
			if(!_aLGO_sortedList[_i_tagIdx].Contains(_aGO_sceneGOs[i]))
			{
				//Ok, add !
				_aLGO_sortedList[_i_tagIdx].Add(_aGO_sceneGOs[i]);
			}
			
		}//for()

		//Done! Now fill-in main 2D array
		for(int j = 0; j < _aLGO_sortedList.Length; j++)
		{
			_aaGO_tags[j] = _aLGO_sortedList[j].ToArray();
			
		}//for()

	}// GetListByTagsFromScene
	
	
	private void GetListByTagsFromProject()
	{
		//Get every gameObject from project folder root Assets
		GameObject[] _aGO_prefabs = GetAllGameObjects(eMainDirectory.Project);
		
		//Get genuine tags list
		_as_tags = UnityEditorInternal.InternalEditorUtility.tags;
		
		//Setup temp list
		List<GameObject>[] _aLGO_GOTag = new List<GameObject>[_as_tags.Length];
		
		//Loop through every gameobjects
		for(int i = 0; i < _aGO_prefabs.Length; i++)
		{
			//Get gameObject.tag'index
			int _i_tagIdx = TagToIndex(_aGO_prefabs[i].tag);
			
			//Not already a List ?
			if(_aLGO_GOTag[_i_tagIdx] == null) _aLGO_GOTag[_i_tagIdx] = new List<GameObject>();
			
			//Not already in the list ?
			if(!_aLGO_GOTag[_i_tagIdx].Contains(_aGO_prefabs[i]))
			{
				//Add gameObject to list
				_aLGO_GOTag[_i_tagIdx].Add(_aGO_prefabs[i]);
			}
			
		}//for()

		//Fill-in empty list
		for(int j = 0; j < _aLGO_GOTag.Length; j++)
		{
			if(_aLGO_GOTag[j] == null) _aLGO_GOTag[j] = new List<GameObject>();
			
		}//for()
		
		//Re-init main array
		_aaGO_tags = new GameObject[_aLGO_GOTag.Length][];
		
		//Re-init bool foldout array
		_ab_foldout_tags = new bool[_aLGO_GOTag.Length];

		//Fill-in main 2D array
		for(int k = 0; k < _aLGO_GOTag.Length; k++)
		{
			//Setup foldout bool array
			_ab_foldout_tags[k] = false;

			//Fill-in main 2D array
			if(_aLGO_GOTag[k] != null) _aaGO_tags[k] = _aLGO_GOTag[k].ToArray();
			
		}//for()
		
	}// GetListByTagsFromProject


	private void GetListByLayersFromScene()
	{
		//Setup main 2D array
		_aaGO_layers = new GameObject[32][];

		//Setup foldout array
		_ab_foldout_layers = new bool[32];

		//Setup temp. array(static layers number)/list(dynamic fill-in gameobjects)
		List<GameObject>[] _aLGO = new List<GameObject>[32];

		//Get all gameobjects from scene
		GameObject[] _aGO = GetAllGameObjects(eMainDirectory.Scene);

		//Fill-in dynamic list
		for(int j = 0; j < _aGO.Length; j++)
		{
			int _i_idx = _aGO[j].layer;

			if(_aLGO[_i_idx] == null) _aLGO[_i_idx] = new List<GameObject>();

			_aLGO[_i_idx].Add(_aGO[j]);
			
		}//for()

		//Format dynamic list into static array
		for(int k = 0; k < 32; k++)
		{
			if(_aLGO[k] != null)
			{
				_aaGO_layers[k] = _aLGO[k].ToArray();
			}

			_ab_foldout_layers[k] = false;

		}//for()

	}// GetListByLayersFromScene
	
	
	private void GetListByLayersFromProject()
	{
		//Get every gameObject from project folder root Assets
		GameObject[] _aGO_prefabs = GetAllGameObjects(eMainDirectory.Project);
		
		//Setup temp list
		List<GameObject>[] _aLGO_GOLayer = new List<GameObject>[32];
		
		//Loop through every gameobjects
		for(int i = 0; i < _aGO_prefabs.Length; i++)
		{
			//Get gameObject.layer'index
			int _i_tagIdx = _aGO_prefabs[i].layer;
			
			//Not already a List ?
			if(_aLGO_GOLayer[_i_tagIdx] == null) _aLGO_GOLayer[_i_tagIdx] = new List<GameObject>();
			
			//Not already in the list ?
			if(!_aLGO_GOLayer[_i_tagIdx].Contains(_aGO_prefabs[i]))
			{
				//Add gameObject to list
				_aLGO_GOLayer[_i_tagIdx].Add(_aGO_prefabs[i]);
			}
			
		}//for()
		
		//Re-init main array
		_aaGO_layers = new GameObject[32][];
		
		//Re-init bool foldout array
		_ab_foldout_layers = new bool[32];
		
		//Fill-in main 2D array
		for(int j = 0; j < _aLGO_GOLayer.Length; j++)
		{
			//Setup foldout bool array
			_ab_foldout_layers[j] = false;
			
			if(_aLGO_GOLayer[j] != null) _aaGO_layers[j] = _aLGO_GOLayer[j].ToArray();
			
		}//for()
		
	}// GetListByLayersFromProject


	private GameObject[] GetAllGameObjects(eMainDirectory _eMD_dir)
	{
		GameObject[] _aGO_GOs = (GameObject[])Resources.FindObjectsOfTypeAll(typeof(GameObject));

		switch(_eMD_dir)
		{
		
		//|| SCENE ||
		case eMainDirectory.Scene:
		{
			//Trim so we get only gameobjects from scene
			List<GameObject> _LGO_sceneGOs = new List<GameObject>();

			for(int i = 0; i < _aGO_GOs.Length; i++)
			{
				PrefabType _PT_type = PrefabUtility.GetPrefabType(_aGO_GOs[i]);
				
				//No genuine Prefab or genuine ModelPrefab
				if(_PT_type != PrefabType.Prefab && _PT_type != PrefabType.ModelPrefab)
				{
					//OK !
					_LGO_sceneGOs.Add(_aGO_GOs[i]);
				}
				
			}//for()

			_aGO_GOs = _LGO_sceneGOs.ToArray();

		}break;
		
		//|| PROJECT ||
		case eMainDirectory.Project:
		{
			//Trim so we get only gameobjects from asset folder
			List<GameObject> _LGO_projectGOs = new List<GameObject>();
			
			for(int i = 0; i < _aGO_GOs.Length; i++)
			{
				PrefabType _PT_type = PrefabUtility.GetPrefabType(_aGO_GOs[i]);

				//Only genuine Prefab or genuine ModelPrefab
				if(_PT_type == PrefabType.Prefab || _PT_type == PrefabType.ModelPrefab)
				{
					//OK !
					_LGO_projectGOs.Add(_aGO_GOs[i]);
				}
				
			}//for()
			
			_aGO_GOs = _LGO_projectGOs.ToArray();

		}break;

		default:break;
		
		}//switch(_eMD_dir)

		return _aGO_GOs;

	}// GetAllGameObjects


	private int TagToIndex(string _s_tag)
	{
		int _i_index = -1;

		string[] _as_tags = UnityEditorInternal.InternalEditorUtility.tags;

		for(int i = 0; i < _as_tags.Length; i++)
		{
			//Found tag ?
			if(_i_index < 0 && string.Compare(_s_tag, _as_tags[i]) == 0)
			{
				_i_index = i;
			}
			
		}//for()

		return _i_index;

	}// TagToIndex


	private string IndexToTag(int _i_index)
	{
		string _s_tag = "";

		string[] _as_tags = UnityEditorInternal.InternalEditorUtility.tags;

		if(_i_index >= 0 && _i_index < _as_tags.Length)
		{
			_s_tag = _as_tags[_i_index];
		}

		return _s_tag;

	}// IndexToTag
	
}// SearchTagLayer