A solution is to create an Item and specify the "Producer" field with a value of "System" (or something that makes sense to you) for each "Supplier" you that would have the fee included on the invoice.
 
You will then need to create an inventory record at each warehouse for that "Wine" and enter an arbitrary quantity. The inventory record needs to exist because that is how Vinosmith groups line items on orders together.
 
To recap - for each supplier:
  1. Add Item with a Producer "System" and mark the Wine as Inventory Item = No. When editing a wine this is a checkbox.
  2. Create a dummy inventory record with your primary warehouse - any quantity is acceptable.
You can now add these "Wines" to invoices.
 

For Distributors at Vinlux Warehouse

All non-inventory items will need to be added to Vinlux. You will need to contact your Vinlux Support Representative and inquire about that process. It's not done in Vinosmith and you would work directly with Vinlux.  The two codes must match.