A solution is to create an Item and assign the "Producer" field as "System" (or another appropriate option) for each "Supplier" whose fee should appear on the invoice.
You will then need to create an inventory record for that "Item" at each warehouse and enter an arbitrary quantity. The inventory record is needed because that is how Vinosmith groups line items on orders.
Non-inventory items will not be included on the repot RC6 - Commissions calculator.
Non-inventory items are not displayed in Global Search results but can be included after performing a search.
To recap - for each supplier:
Add Item with a Producer "System" and mark the Wine as Inventory Item = No
Create a dummy inventory record with your primary warehouse - any quantity is acceptable. The inventory record must exist because that is how Vinosmith groups line items on orders.
You can now add these Items to invoices.
For Distributors at Vinlux Warehouse (California)
All non-inventory items must be added to Vinlux. You will need to contact your Vinlux Support Representative and inquire about that process. It's not done through Vinosmith; you would work directly with Vinlux. The two codes must match.