+using System.Text.RegularExpressions;

+  static readonly Regex rArrayItemProp = new Regex(@"\.Array\.data\[(\d+)\]$");

+    if (property.name == "data") {

+      var matchArrayItem = rArrayItemProp.Match(property.propertyPath);

+      if (matchArrayItem.Success) // property is array item

+        label.text = "Element " + matchArrayItem.Groups[1].Value; // label should not be GUID in array item

+    }

+    // NOTE: doesn't handle missing references, which are shown as "None (Scene Asset)"

+    var preloaded = PlayerSettings.GetPreloadedAssets();

+    if (preloaded != null) {

+    base.hideFlags = HideFlags.NotEditable;

+  public int sceneIndex { get {

+    var s = UnityEditor.EditorBuildSettings.scenes;

+    for (int i = 0, n = s.Length; i < n; i++)

+      if (s[i].guid.ToString() == sceneGuid) return i;

+    return -1;

+  } }

+    if (PlayerSettings.GetPreloadedAssets() is {} preloaded) {

+      int n = preloaded.Length - 1, i = n;

+      for (; i >= 0; i--) if (preloaded[i] is SceneReferences) break; // i = Array.FindLastIndex

+      if (i >= 0) {

+        var newPreloaded = new UnityEngine.Object[n];

+        Array.Copy(preloaded, newPreloaded, i);

+        Array.Copy(preloaded, i + 1, newPreloaded, i, n - i);

+        PlayerSettings.SetPreloadedAssets(newPreloaded);

+      }

+  ///<param name="sceneGuid">The GUID of the scene to look up.</param>

+  ///<summary>Create a reference to a scene using its GUID.</summary>

+  ///<param name="guid">The GUID of the scene, found in its .scene.meta file, or obtained from AssetDatabase.</param>

+  public SceneReference(Guid guid) => this.sceneGuid = guid;

+    if (i >= 0) {

+      var n = preloaded.Length - 1;

+      var newPreloaded = new UnityEngine.Object[n];

+      Array.Copy(preloaded, newPreloaded, i);

+      Array.Copy(preloaded, i + 1, newPreloaded, i, n - i);

+      PlayerSettings.SetPreloadedAssets(newPreloaded);

+    }

+    AssetDatabase.DeleteAsset(resourcePath);

+    AssetDatabase.SaveAssets();

+

+using UnityEngine;

+using UnityEditor;

+

+[CustomPropertyDrawer(typeof(SceneReference))]

+public class SceneReferenceDrawer : PropertyDrawer

+{

+  public override void OnGUI(Rect position, SerializedProperty property, GUIContent label) {

+    if (!property.NextVisible(true)) return;

+    // could use 128-bit type to serialize, like rectIntValue; but it would be less legible in text assets

+    var oldGuid = property.stringValue;

+    var oldPath = AssetDatabase.GUIDToAssetPath(oldGuid);

+    var oldObj = AssetDatabase.LoadAssetAtPath<SceneAsset>(oldPath);

+    var newObj = EditorGUI.ObjectField(position, label, oldObj, typeof(SceneAsset), false) as SceneAsset;

+    if (newObj == oldObj) return;

+    if (newObj == null)

+      property.stringValue = "";

+    else if (AssetDatabase.TryGetGUIDAndLocalFileIdentifier(newObj, out string newGuid, out long _))

+      property.stringValue = newGuid;

+  }

+

+using System;

+using UnityEditor;

+using UnityEditor.Build;

+using UnityEditor.Build.Reporting;

+using UnityEngine;

+

+class SceneReferencesBuildProcessor : IPreprocessBuildWithReport, IPostprocessBuildWithReport

+{

+  const string resourcePath = "Assets/_autoBuild_SceneIndicesByGuid.asset";

+  public int callbackOrder => 0;

+  public void OnPreprocessBuild(BuildReport report) {

+    var sceneReferences = ScriptableObject.CreateInstance<SceneReferences>();

+    AssetDatabase.CreateAsset(sceneReferences, resourcePath);

+    var preloaded = PlayerSettings.GetPreloadedAssets();

+    var n = preloaded.Length;

+    Array.Resize(ref preloaded, n + 1);

+    preloaded[n] = sceneReferences;

+    PlayerSettings.SetPreloadedAssets(preloaded);

+  }

+  public void OnPostprocessBuild(BuildReport report) {

+    AssetDatabase.DeleteAsset(resourcePath);

+    var preloaded = PlayerSettings.GetPreloadedAssets();

+    var i = Array.FindLastIndex(preloaded, o => o is SceneReferences);

+    if (i < 0) return;

+    var n = preloaded.Length - 1;

+    var newPreloaded = new UnityEngine.Object[n];

+    Array.Copy(preloaded, newPreloaded, i);

+    Array.Copy(preloaded, i + 1, newPreloaded, i, n - i);

+    PlayerSettings.SetPreloadedAssets(newPreloaded);

+  }

+

+using System;

+using System.Collections.Generic;

+using UnityEngine;

+using Guid = System.String; // could use 128-bit int type to serialize, but it would be less legible in text assets

+

+///<summary>SceneReferences contains the GUID to build index mapping, used to reference scenes at runtime.</summary>

+///<remarks>This is auto-generated on build as a preloaded asset.</remarks>

+public class SceneReferences : ScriptableObject

+{

+  ///<summary>The singleton instance, automatically preloaded at runtime.</summary>

+  public static SceneReferences instance => asset

+#if UNITY_EDITOR

+  ?? (asset = ScriptableObject.CreateInstance<SceneReferences>())

+#endif

+  ; static SceneReferences asset;

+  ///<summary>The GUID for each scene asset, indexed by its build index in the array.</summary>

+  public Guid[] guids => sceneGuids; [SerializeField] Guid[] sceneGuids;

+  Dictionary<Guid, int> cache;

+  private void Awake() {

+#if UNITY_EDITOR

+    sceneGuids = Array.ConvertAll(UnityEditor.EditorBuildSettings.scenes, s => s.guid.ToString());

+#endif

+    if (sceneGuids == null) sceneGuids = new Guid[0];

+    int n = sceneGuids.Length;

+    cache = new Dictionary<Guid, int>(n);

+    for (int i = 0; i < n; i++)

+      cache.Add(sceneGuids[i], i);

+    asset = this;

+  }

+  ///<summary>The build index of a scene by GUID. It can be used to load it or to obtain scene info.</summary>

+  ///<remarks>All mappings are cached on a dictionary when the asset is preloaded at startup.</remarks>

+  public int SceneIndex(Guid sceneGuid) => cache.TryGetValue(sceneGuid, out int i) ? i : -1;

+}

+

+///<summary>SceneReference is used to reference a Scene by its guid at runtime.</summary>

+[Serializable]

+public struct SceneReference

+{

+  ///<summary>The GUID that uniquely identifies this scene asset, used to serialize scene references reliably.</summary>

+  ///<remarks>Even if you move/rename the scene asset, GUID references stay valid.</remarks>

+  public Guid guid => sceneGuid; [SerializeField] Guid sceneGuid;

+  ///<summary>The build index of this scene, which can be used to load it or to obtain scene info.</summary>

+#if UNITY_EDITOR

+  public int sceneIndex => this.sceneGuid switch {

+    var sceneGuid => Array.FindIndex(UnityEditor.EditorBuildSettings.scenes, s => s.guid.ToString() == sceneGuid)

+  };

+#else

+  public int sceneIndex => SceneReferences.instance.SceneIndex(sceneGuid);

+#endif