Custom Fields are additional columns that can be filled in with numeric, text or currency info. You can reference custom fields in smart lists, exports, and pricing rules. To add a new Custom Field click on the 'add new' button under all existing custom fields.
Only 'money' fields can be used in pricing rules. You can edit the value of an item's custom field through a file upload or in the inventory grid.
You can create as many custom fields as needed. If a custom field is used as a filter of a smart list, in a pricing rule, etc., you won't be able to delete it, not even by mistake.