Hi Hidyath,
After BTE implementation, you need to write a small enhancement to achieve your requirement, please review the OSS note 984305 - Line item: Definition of special fields (T021S), with the help of your ABAPER to achieve your requirement.
Or follow the instructions in the link Enhancing SAP standard transactions FBL3N/FBL1N/FBL5N with extra fields in the output list via BTEto achieve your requirement.
REgards,
Ravi