These preferences allow you to determine if the software will allow to create multiple wiring equipment items or just one item under a vacant slot.
To access these preferences, in the Preferences dialog, in the tree view pane, select beside Wiring and then select I/O Card.
Assign slots for racks
All slots (vacant and occupied)
Allows you to create multiple wiring equipment items or double-width I/O cards under vacant slots.
Vacant slots only
Allows you to create only one wiring equipment item per vacant slot. The software will not allow you to add a double-width card or another wiring equipment item under an occupied slot.