contract/agreement_sale/views/sale_order.xml

<?xml version="1.0"?>
<!--
  © 2017 Akretion (Alexis de Lattre <alexis.delattre@akretion.com>)
  License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
-->

<odoo>


<record id="view_order_form" model="ir.ui.view">
    <field name="name">agreement.sale.order.form</field>
    <field name="model">sale.order</field>
    <field name="inherit_id" ref="sale_commercial_partner.view_order_form"/>
    <field name="arch" type="xml">
        <field name="client_order_ref" position="after">
            <field name="agreement_id"
                domain="[('partner_id', 'child_of', commercial_partner_id), ('agreement_type', '=', 'sale')]"
                context="{'default_partner_id': commercial_partner_id, 'default_agreement_type': 'sale'}"/>
        </field>
    </field>
</record>

<record id="view_sales_order_filter" model="ir.ui.view">
    <field name="name">agreement.sale.order.search</field>
    <field name="model">sale.order</field>
    <field name="inherit_id" ref="sale.view_sales_order_filter"/>
    <field name="arch" type="xml">
        <group expand="0" position="inside">
            <filter string="Agreement" name="agreement_groupby" context="{'group_by': 'agreement_id'}"/>
        </group>
    </field>
</record>


</odoo>