Improve #2100 and fix undo

Source/Editor/Modules/SceneEditingModule.cs

@@ -542,24 +542,27 @@ namespace FlaxEditor.Modules
             Actor actor = new EmptyActor();
             Editor.SceneEditing.Spawn(actor, null, false);
             List<SceneGraphNode> selection = Editor.SceneEditing.Selection;
-            for (int i = 0; i < selection.Count; i++)
+            var actors = selection.Where(x => x is ActorNode).Select(x => ((ActorNode)x).Actor);
+            using (new UndoMultiBlock(Undo, actors, "Reparent actors"))
             {
-                if (selection[i] is ActorNode node)
+                for (int i = 0; i < selection.Count; i++)
                 {
-                    if (node.ParentNode != node.ParentScene) // if parent node is not Scene
+                    if (selection[i] is ActorNode node)
                     {
-                        if (selection.Contains(node.ParentNode))
+                        if (node.ParentNode != node.ParentScene) // If parent node is not a scene
                         {
-                            return; // if parent and child nodes selected together, don't touch child nodes
-                        }
-                        else
-                        {   // put created node as child of the Parent Node of node
+                            if (selection.Contains(node.ParentNode))
+                            {
+                                return; // If parent and child nodes selected together, don't touch child nodes
+                            }
+
+                            // Put created node as child of the Parent Node of node
                             int parentOrder = node.Actor.OrderInParent;
                             actor.Parent = node.Actor.Parent;
                             actor.OrderInParent = parentOrder;
                         }
+                        node.Actor.Parent = actor;
                     }
-                    node.Actor.Parent = actor;
                 }
             }
             Editor.SceneEditing.Select(actor);

Source/Editor/Modules/UIModule.cs

@@ -549,13 +549,11 @@ namespace FlaxEditor.Modules
             _menuEditCut = cm.AddButton("Cut", inputOptions.Cut, Editor.SceneEditing.Cut);
             _menuEditCopy = cm.AddButton("Copy", inputOptions.Copy, Editor.SceneEditing.Copy);
             _menuEditPaste = cm.AddButton("Paste", inputOptions.Paste, Editor.SceneEditing.Paste);
-            cm.AddSeparator();
-            _menuCreateParentForSelectedActors = cm.AddButton("Create parent for selected actors", Editor.SceneEditing.CreateParentForSelectedActors);
-            cm.AddSeparator();
             _menuEditDelete = cm.AddButton("Delete", inputOptions.Delete, Editor.SceneEditing.Delete);
             _menuEditDuplicate = cm.AddButton("Duplicate", inputOptions.Duplicate, Editor.SceneEditing.Duplicate);
             cm.AddSeparator();
             _menuEditSelectAll = cm.AddButton("Select all", inputOptions.SelectAll, Editor.SceneEditing.SelectAllScenes);
+            _menuCreateParentForSelectedActors = cm.AddButton("Create parent for selected actors", Editor.SceneEditing.CreateParentForSelectedActors);
             _menuEditFind = cm.AddButton("Find", inputOptions.Search, Editor.Windows.SceneWin.Search);
             cm.AddSeparator();
             cm.AddButton("Game Settings", () =>

Source/Editor/Windows/SceneTreeWindow.ContextMenu.cs

@@ -132,17 +132,13 @@ namespace FlaxEditor.Windows
             b = contextMenu.AddButton("Cut", inputOptions.Cut, Editor.SceneEditing.Cut);
             b.Enabled = canEditScene;
 
-            // Create a new hierarchy from selected actors 
+            // Create option
 
             contextMenu.AddSeparator();
 
             b = contextMenu.AddButton("Create parent for selected actors", Editor.SceneEditing.CreateParentForSelectedActors);
             b.Enabled = canEditScene && hasSthSelected;
 
-            // Prefab options
-
-            contextMenu.AddSeparator();
-
             b = contextMenu.AddButton("Create Prefab", Editor.Prefabs.CreatePrefab);
             b.Enabled = isSingleActorSelected &&
                         ((ActorNode)Editor.SceneEditing.Selection[0]).CanCreatePrefab &&