partner-contact/partner_contact_access_link/views/res_partner_views.xml

<?xml version="1.0" encoding="utf-8" ?>
<!-- Copyright 2020 Tecnativa - Jairo Llopis
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->
<data>
    <record id="view_partner_form" model="ir.ui.view">
        <field name="name">Add button to see child contacts full form</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_partner_form" />
        <field name="arch" type="xml">
            <!-- Make child kanban able to open form in full view -->
            <xpath
                expr="//field[@name='child_ids']/kanban/templates//field[@name='name']"
                position="after"
            >
                <button
                    class="btn btn-link"
                    type="object"
                    name="open_child_form"
                    title="Open full form"
                >
                    <i class="fa fa-external-link-square" />
                </button>
            </xpath>
        </field>
    </record>
</data>