Added ability to keep folders in Playmode

Author: neon-age

Base/DetachOnBuildProcess.cs

@@ -14,6 +14,11 @@ internal class DetachOnBuildProcess : IProcessSceneWithReport
 
         public void OnProcessScene(Scene scene, BuildReport report)
         {
+            var preferences = HierarchySettingsProvider.GetProvider().preferences;
+
+            if (Application.isEditor && preferences.keepFoldersInPlaymode)
+                return;
+            
             var sceneRoots = scene.GetRootGameObjects();
             foreach (var root in sceneRoots)
             {

Base/HierarchySettingsProvider.cs

@@ -26,6 +26,7 @@ internal class HierarchyPreferences : ScriptableObject
         public bool enableSmartHierarchy = true;
         public StickyIcon stickyComponentIcon = StickyIcon.NotOnPrefabs;
         public TransformIcon transformIcon = TransformIcon.OnUniqueOrigin;
+        public bool keepFoldersInPlaymode;
     }
 
     internal class HierarchySettingsProvider : SettingsProvider

README.md

@@ -14,9 +14,11 @@ Note: Icons are not attached to Prefabs root. This behaviour can be changed in P
 
 Folder is a special Editor-only object that has no components and no transform.\
 It detaches it's children on scene process, so there is no overhead at runtime.\
+[Best Practices: Transforms Optimization](https://unity.com/ru/how-to/best-practices-performance-optimization-unity#transforms) \
 [Best Practices: Optimizing the Hierarchy](https://blogs.unity3d.com/ru/2017/06/29/best-practices-from-the-spotlight-team-optimizing-the-hierarchy/)
 
-**Issue:** Currently there is no folders displayed in Playmode.
+**Issue:** Currently folders are not displayed in Playmode.\
+There is an option (in Preferences) to keep them in Editor, but beware of the overhead.
 
 ### Activation Toggle
 ![Activation Toggle](https://i.imgur.com/nv7aPE5.png)

UI/smart_hierarchy_settings.uxml

@@ -6,5 +6,8 @@
             <uie:EnumField label="Sticky Component Icon" binding-path="stickyComponentIcon" tooltip="Main component icon that is shown instead of GameObject or Prefab icon." />
             <uie:EnumField label="Transform Icon" binding-path="transformIcon" />
         </ui:Foldout>
+        <ui:Foldout text="Folders">
+            <ui:Toggle label="Keep In Playmode" binding-path="keepFoldersInPlaymode" />
+        </ui:Foldout>
     </ui:VisualElement>
 </ui:UXML>