If you have any Supplier User you no longer want to see your collection - you can Deactivate him.
Simply mouse over the supplier row and click the blue edit icon - or double-click on the table row.
When in edit mode, click the 'Select brand' drop-down and remove the brand assigned to the supplier.
Now, this Supplier User can no longer see anything in your collection.
If you for some reason have a Supplier User that you do not need anymore - you can delete him.
Simply move your cursor over the name of the Supplier User and then click on the Delete button. The user will be removed from your Supplier list.