EZ Inventory has supported using formulas for inventory quantity updates for quite some time now.  This allowed our users to use conditional logic and other data manipulation against their supplier feed's data when updating the quantity in Shopify.

We've just pushed an update to extend this functionality for mapping items from their supplier's feed to product variants in their Shopify store.  This option is now available in the Data Feed settings:

Since most merchants don't have the option to modify or customize …