partner-contact/partner_deduplicate_by_ref/wizards/partner_merge_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2017 Pedro M. Baeza <pedro.baeza@tecnativa.com>
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html). -->

<odoo>

    <record id="base_partner_merge_automatic_wizard_form" model="ir.ui.view">
        <field name="model">base.partner.merge.automatic.wizard</field>
        <field name="inherit_id" ref="base.base_partner_merge_automatic_wizard_form"/>
        <field name="arch" type="xml">
            <field name="group_by_parent_id" position="after">
                <field name="group_by_ref"/>
            </field>
            <xpath expr="//field[@name='partner_ids']/tree//field[@name='country_id']" position="after">
                <field name="ref"/>
            </xpath>
        </field>
    </record>

</odoo>