Use the Hierarchy window to add new GameObjects to a scene and duplicate existing GameObjects. To group GameObjects into parent-child hierarchies, refer to Manage GameObjects in the Hierarchy window.
You can set where new GameObjects are created in a scene from the Scene view preferences by selecting an option for 3D Placement Mode.
By default, Unity creates new GameObjects in rename mode. To disable this behavior, open the More (⋮) menu in the Hierarchy window and deselect Rename New Objects.
To create a new GameObject in the Hierarchy window:
Tip: Press Ctrl+Shift+N (macOS: Cmd+Shift+N) to create an empty GameObject.
To duplicate a GameObject, right-click the target GameObject and select Duplicate.
You can also use the keyboard shortcut Ctrl+D (macOS: Cmd+D).