Let me share information about importing an inventory with a preferred supplier, @MelD50.
To begin with, please know that the direct import process in QuickBooks Online doesn’t include the Preferred Supplier field yet.
However, since you want to import 6000 inventory line items, I suggest using a third-party app that integrates with QuickBooks to save time.
Additionally, if you need to track your stock, please refer to this article: Set up and track your stock.
If you encounter further issues while importing inventory, please let me know. Good luck with your inventory management. Keep safe.
