Custom Fields Missing

I’m using WP All Import for 500+ products and for some reason there is no custom field for ‘Up-Sells’ for me to populate the field with SKUs from the database. The is one for ‘Cross-Sells’ which works perfectly. Do I need to do something to get that field to show up? Or does it have a unique name that I can just type into the custom fields name?

Thanks for any help!