manufacture/mrp_subcontracting_inhibit/views/purchase_order_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>

    <record id="view_order_form_inherit_purchase_order" model="ir.ui.view">
        <field name="name">purchase.order.view.form.inherit</field>
        <field name="model">purchase.order</field>
        <field name="inherit_id" ref="purchase.purchase_order_form" />
        <field name="arch" type="xml">
            <xpath
                expr="//field[@name='order_line']/tree/field[@name='product_id']"
                position="after"
            >
                <field name="subcontracting_inhibit" optional="show" />
            </xpath>
        </field>
    </record>


</odoo>