manufacture/mrp_production_request/views/mrp_production_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<!-- Copyright 2017 ForgeFlow S.L.
     License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl-3.0) -->
<odoo>
    <record id="mrp_production_form_view" model="ir.ui.view">
        <field name="name">mrp.production.form - mrp_production_request</field>
        <field name="model">mrp.production</field>
        <field name="inherit_id" ref="mrp.mrp_production_form_view" />
        <field name="arch" type="xml">
            <xpath expr="//form/sheet/notebook/page[3]/group" position="after">
                <group>
                    <field name="mrp_production_request_id" />
                </group>
            </xpath>
        </field>
    </record>
</odoo>