Is it possible to reference the "Preferred Vendor" field on the item record via workflows.

It is possible to reference the "Preferred Vendor" field on the item record via workflows when Multiple Vendors is set to False ( Setup > Company > Enable Features > Items & Inventory > Multiple Vendors == 'F' ). 

Wheter Multiple Vendors is set to true or false, the preferred vendor field is displayed as a sub list and therefore it can no longer be referenced by workflows.