<odoo>
    <record id="account_payment_order_manual_email_form" model="ir.ui.view">
        <field name="name">account_payment_order_manual_email_form</field>
        <field name="model">account.payment.order</field>
        <field
            name="inherit_id"
            ref="account_payment_order.account_payment_order_form"
        />
        <field name="arch" type="xml">
            <button name="action_uploaded_cancel" position="after">
                <button
                    name="send_vendor_email"
                    string="Send Email"
                    type="object"
                    class="oe_highlight"
                    states="uploaded"
                />
            </button>
        </field>
    </record>
</odoo>
