partner-contact/partner_mobile_unique/views/res_config_settings_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="view_general_configuration_mobile_check_unique" model="ir.ui.view">
        <field name="name">partner_mobile_unique</field>
        <field name="model">res.config.settings</field>
        <field name="inherit_id" ref="base_setup.res_config_settings_view_form" />
        <field name="arch" type="xml">
            <xpath expr="//div[@id='companies']" position='after'>
                <h2>Mobile validation</h2>
                <div class="row mt16 o_settings_container" name="partner_mobile_unique">

                    <div class="col-xs-12 col-md-6 o_setting_box">
                        <div class="o_setting_left_pane">
                            <field name="partner_mobile_unique_filter_duplicates" />
                        </div>
                        <div class="o_setting_right_pane">
                            <label for="partner_mobile_unique_filter_duplicates" />
                            <span
                                class="fa fa-lg fa-building-o"
                                title="Values set here are company-specific."
                                aria-label="Values set here are company-specific."
                                groups="base.group_multi_company"
                                role="img"
                            />
                            <div class="text-muted">
                                Require partner mobile number to be unique
                            </div>
                        </div>
                    </div>

                </div>
            </xpath>
        </field>
    </record>
</odoo>