oca-technical/odoo-bringout-oca-crm-crm_phonecall/crm_phonecall/views/crm_lead_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <!-- This view is there, but it is not used in the CRM Menus -->
    <record id="crm_case_form_view_leads_inherit" model="ir.ui.view">
        <field name="name">CRM - Leads Form</field>
        <field name="model">crm.lead</field>
        <field name="inherit_id" ref="crm.crm_lead_view_form" />
        <field name="arch" type="xml">
            <xpath expr="//div[@name='button_box']" position="inside">
                <button
                    class="oe_stat_button"
                    icon="fa-phone"
                    name="button_open_phonecall"
                    type="object"
                >
                    <field name="phonecall_count" string="Calls" widget="statinfo" />
                </button>
            </xpath>
        </field>
    </record>
</odoo>