whatsapp_web_groups/views/whatsapp_account_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record id="whatsapp_account_view_form_custom" model="ir.ui.view">
        <field name="name">whatsapp.account.view.form.custom</field>
        <field name="model">whatsapp.account</field>
        <field name="inherit_id" ref="whatsapp.whatsapp_account_view_form"/>
        <field name="arch" type="xml">
            <!-- Agregamos una nueva sección al final del <sheet> -->
            <sheet position="inside">
                <div class="o_horizontal_separator mt-4 mb-3 text-uppercase fw-bolder small">
                    WhatsApp Web
                </div>
                <group>
                    <field name="whatsapp_web_url" placeholder="e.g. https://web.whatsapp.com/"/>
                </group>
            </sheet>
        </field>
    </record>
</odoo>