Also I believe you can press F4 to duplicate the currently selected object/button. F3 to create a new object/button. ctrl/cmd + c to copy the currently selected object/button & ctrl/cmd + v to paste it.
I also second what Sebastian just said, it's far easier to create one slot then just duplicate or copy/paste it a bunch of times & reposition the polygon area for each one. If you move the cursor to the center of the polygon & hold down ctrl/cmd then you can drag the whole polygon around by left clicking & dragging or you can tap the left mouse button to select the whole polygon & then use the arrow keys on your keyboard to nudge/move the polygon around.