partner-contact/partner_pricelist_search/views/product_pricelist_views.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="product_pricelist_view" model="ir.ui.view">
        <field name="model">product.pricelist</field>
        <field name="inherit_id" ref="product.product_pricelist_view" />
        <field name="arch" type="xml">
            <widget name="web_ribbon" position="before">
                <div class="oe_button_box" name="button_box">
                    <button
                        name="show_pricelist_partners"
                        type="object"
                        string="Customers"
                        class="oe_stat_button"
                        icon="fa-users"
                    />
                </div>
            </widget>
        </field>
    </record>
</odoo>