Enabling DFF in AR Transaction Workbench

All,requirement is to capture a flag at transaction level (Header) which will decide whether Invoice print copy need to be delivered to Customer.

To achieve this I can enable a transaction header level DFF and this will meet the requirement for Manual transactions.

Let's say DFF will be enabled on ra_customer_trx.attribute1

My question is, how can we capture this value for Imported transactions?. Should we populate the attribute1 of ra_interface_lines_all table?. In that case, Doesn't Autoinvoice consider this as a line level detail?.

Thanks