Re: defaulting header texts in ME21n texts tab

• Did you have a check on BADI, ME_PROCESS_PO_CUST?
• Using the method,  PROCESS_HEADER. would be handy for your requirement. Interface: IF_PURCHASE_ORDER_MM and use method IF_LONGTEXTS_MM-SET_TEXT.
• Read the documentation of this BADI.

Regards,

Philip.