Update

Assets/Third Parties/D.A. Assets/DA-Shared/Runtime/Extensions/ReflectedExtensions.cs

@@ -0,0 +1,47 @@
+using UnityEngine;
+using UnityEngine.SceneManagement;
+
+namespace DA_Assets.Extensions
+{
+    public static class ReflectedExtensions 
+    {
+        /// <summary>
+        /// <para><see href="https://forum.unity.com/threads/how-to-collapse-hierarchy-scene-nodes-via-script.605245/#post-6551890"/></para>
+        /// </summary>
+        public static void SetExpanded(this Scene scene, bool expand)
+        {
+#if UNITY_EDITOR
+            foreach (var window in Resources.FindObjectsOfTypeAll<UnityEditor.SearchableEditorWindow>())
+            {
+                if (window.GetType().Name != "SceneHierarchyWindow")
+                    continue;
+
+                var method = window.GetType().GetMethod("SetExpandedRecursive",
+                    System.Reflection.BindingFlags.Public |
+                    System.Reflection.BindingFlags.NonPublic |
+                    System.Reflection.BindingFlags.Instance, null,
+                    new[] { typeof(int), typeof(bool) }, null);
+
+                if (method == null)
+                {
+                    Debug.LogError(
+                        "Could not find method 'UnityEditor.SceneHierarchyWindow.SetExpandedRecursive(int, bool)'.");
+                    return;
+                }
+
+                var field = scene.GetType().GetField("m_Handle",
+                    System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
+
+                if (field == null)
+                {
+                    Debug.LogError("Could not find field 'int UnityEngine.SceneManagement.Scene.m_Handle'.");
+                    return;
+                }
+
+                var sceneHandle = field.GetValue(scene);
+                method.Invoke(window, new[] { sceneHandle, expand });
+            }
+#endif
+        }
+    }
+}