Hello Talmid,

    I have the solution for your problem if you're still need it. I created a modul to solve this problem and it's working proprely, I have a little issu to add the partner to the header template, but i'll fixe it soon.

that's the code a added.

@api.model
def _get_partner(self, move_line):
    partner = ''
    partner_id = False
    picking_id = move_line.picking_id or move_line.move_id.picking_id
    if picking_id:
        partner_id = picking_id.partner_id.id
        partner = picking_id.partner_id.name
    return partner