whatsapp_web_groups/views/whatsapp_composer_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <!-- Extender vista de formulario del composer de WhatsApp para agregar campo Many2one -->
        <record id="whatsapp_composer_view_form_groups_m2o" model="ir.ui.view">
            <field name="name">whatsapp.composer.view.form.groups.m2o</field>
            <field name="model">whatsapp.composer</field>
            <field name="inherit_id" ref="whatsapp_web.whatsapp_composer_view_form_groups"/>
            <field name="arch" type="xml">
                <!-- Agregar campo Many2one whatsapp_group_id antes de whatsapp_group_id_char -->
                <xpath expr="//field[@name='whatsapp_group_id_char']" position="before">
                    <field name="whatsapp_group_id" 
                           invisible="recipient_type != 'group'"
                           string="WhatsApp Group"
                           placeholder="Select a WhatsApp group..."
                           options="{'no_create': True}"/>
                </xpath>
            </field>
        </record>
    </data>
</odoo>