Tracking Categories per Supplier Invoice Product Transaction Line

Hi,

We have allot of clients on Sage who are using Project Tracking (AKA Tracking Categories in Xero) in order to move them to Dear they would require the tracking category drop downs per inventory line on the Supplier and Customer Invoices.   The same inventory item may be allocated to different projects on the same invoice.  At the moment Dear is very limited.  Please can you help...