partner-contact/partner_stage/views/res_partner_views.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>

    <record id="view_partner_form" model="ir.ui.view">
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_partner_form" />
        <field name="arch" type="xml">
            <sheet position="before">
                <header>
                     <field
                        name="stage_id"
                        widget="statusbar"
                        options="{'clickable': '1', 'fold_field': 'fold'}"
                    />
                </header>
            </sheet>
        </field>
    </record>

    <record id="view_partner_search" model="ir.ui.view">
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_res_partner_filter" />
        <field name="arch" type="xml">
            <filter name="group_country" position="after">
                <filter
                    name="group_country"
                    string="Stage"
                    context="{'group_by': 'stage_id'}"
                />
            </filter>
        </field>
    </record>

</odoo>