Below is a Code to record value in customize field on Sales order packing slip in Axapta. This code is taken form Ax 2012 version but you can try in D365 also.
You need to make changes in method of InitHeader of class SalesPackingSlipJournalCreate . Happy daxing friends.
\Classes\SalesPackingSlipJournalCreate\initHeader
You need to make changes in method of InitHeader of class SalesPackingSlipJournalCreate . Happy daxing friends.
\Classes\SalesPackingSlipJournalCreate\initHeader