Duplicating a slot with a mesh hides the mesh in the new slot.
Steps:
(1) Add an image to the project (adds a slot and an attachment).
(2) Make that image a mesh.
(3) Duplicate that mesh's slot.
(4) Expand the new/duplicated slot (the mesh is hidden)
"Hidden" meaning the visibility dot is off./The setup mode attachment of the new slot is empty.