Variant configuration copy from sales order to return order

Hi,

We create sales order with sales BOM. Both parent material and sub items ( components) are configurable materials.

When we create return sales order with reference to this  original order, system allows item selection at parent material level only. If customer wants to return only one component material , we are not able to return order only for this component but we have to create return order for whole BOM structure.

So we are programatically removing High level relations ( VBAP-UEPOS) and making all items selectable. but when we do so, material configuration for sub items is not getting copied since we have broken linkage between sales order parent material and sub items.

So if we have to add / copy configuration for sub items from original sales order to return order, which tables can provide this infomration?

Thanks

Manoj