Template Items Import Scenario - 3rd Variant Attribute under the Item Creation Tab

I have a scenario where We are creating Template Items and then generating the Matrix Items. We have thousands of template items like this so will be creating many more thousands of matrix items. 

The issue I have is that we are able to, via import scenario, set the Column Attribute ID and Row Attribute ID on the Configuration Tab. These values then carry over to the Item Creation Tab. 

However, in the Item Class we have a 3rd Variant Attribute we want to use which we want to set the value to via import scenario and then trigger the Create Matrix Items button. 

Via Import Scenario how do I target and set a value to these additional Variant Attribute fields. 

 

I can’t find anyway to do it via Import Scenario when the Screen Name is set to Template Item