Moving an item to another item slot

To remove the necklace mesh you will actually have to remove it in blender and make sure that the backpack has the correct cut numbers that match up to the necklace that you use as a base.
So if the necklace you clone has just one group called studio_mesh_0 with a cut nuber of 0, for example, the backpack mesh that you import into studio must also just have one group with the same name and cut number.