odoo/addons/purchase/stock_view.xml

<?xml version="1.0" encoding="utf-8"?>
<terp>
    <data>
        
        <record id="stock_picking_inherit_purchase" model="ir.ui.view">
            <field name="name">Packing list</field>
            <field name="model">stock.picking</field>
            <field name="type">form</field>
            <field name="inherit_id" ref="stock.view_picking_form"/>
            <field name="arch" type="xml">
                <field name="active" position="after">
                    <field name="purchase_id"/>
                </field>
            </field>
        </record>
        
        <act_window domain="[('purchase_id', '=', active_id)]" id="act_purchase_order_2_stock_picking" name="Packings" res_model="stock.picking" src_model="purchase.order"/>
        
    </data>
</terp>