Fetch a commerce line attribute value to config attribute during Asset Modify operation

Summary:

We have setup a Advanced BOM Mapping rule to pass values from config to commerce line attributes under section "From Configuration to BOM". Now when we modify the asset user is redirected directly to the configuration UI. At this point we want to fetch a commerce line attribute value to config attribute. How can this be achieved. I am aware of BOM to configuration section within advanced BOM Mapping rule but can this be used for our requirement since we want to fetch line attrib value? Any sample code snippet will help.

Or is there a way to fetch root asset field value from Asset DB in configuration during modify operation?