<odoo>
    <record id="sales_po_sale_order_custom" model="ir.ui.view">
        <field name="name">sale.order.sales.po.custom</field>
        <field name="model">sale.order</field>
        <field name="inherit_id" ref="sale.view_order_form" />
        <field name="arch" type="xml">
            <field name="client_order_ref" position="after">
                <field name="customer_need_po" readonly="1" />
                <field name="sale_doc" readonly="1" />
                <field
                    invisible="not sale_doc and not sale_document_option"
                    name="sale_document_option"
                />
                <field
                    invisible="not sale_doc and not sale_document_option"
                    name="sale_document_note"
                />
            </field>
        </field>
    </record>
</odoo>
