Unassigned Items
The Collection field is mandatory to create an Item in a Shared Vault. However, an Item can be removed from a Collection after it is created.
If an item is no longer assigned to any Collections, it is added to the Unassigned Collection. This will happen if all all collections that an item is assigned to are unselected or deleted.
This will happen if an Item is Removed from all Collections or if the Collections to which it is assigned are deleted.