The LevelEditor duplicates game objects if you press the SHIFT and CTRL keys while you click the Move manipulator. You can then drag the Move manipulator to position the new game objects in the Design View.
If you duplicate a set of game objects, the objects maintain the same relative positions as they had in the original set. For example, in the figure below, the selected game objects are duplicates of the others. The duplicate game objects have the same relative positions as the original game objects.
To duplicate game objects:
For a demonstration of how to duplicate game objects using the LevelEditor, view the “Duplicating Objects” video, either on the GitHub site or on SHIP.