IDOC - segment Qualifier

Dear all,

Do you know the transaction or an document which give the link between the Qualifier segment of an segment IDOC and the SAP field ?

for example : IDOC ORDERS05

segment E1EDK03

qualifier 002 : wished delivery date in VA01

segment E1EDK02

qualifier 050 : Delivery Order in segment description but correspond to PO number in VA01

I search to fill in the field PO Date but I don't find the qualifer segment.

Could you please help me ?

thanks

Véronique