WebADI - Manage Item Instances

I am planning to use WebADI - Manage Item Instances feature to mass load products that were missed during IB conversion.   When I test the functionality, I don't see anyway to link parent and child record to load configurations. I have ATO Model and ATO Configured Items.

Parent Instance LOV in the spreadsheet points to an existing value. Since this is a new load, I don't have Parent Instance value.  Root Instance field is not update able. 

If neither parent nor root instance field can be populated, how will system know what to build as parent-child record in IB.

Am I missing something or does WebADI functionality is deficient in creating new parent and child association when loading both records.  If it is a gap in the functionality, is there a workaround available to link parent and child records to be loaded using WebADI