stock-logistics-warehouse/stock_cycle_count/views/stock_location_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2017 Eficent Business and IT Consulting Services S.L.
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl). -->

<odoo>

    <record model="ir.actions.act_window" id="act_accuracy_stats">
        <field name="domain">[('location_id', '=', active_ids),
            ('state', '=', 'done')]</field>
        <field name="name">Accuracy Stats</field>
        <field name="res_model">stock.inventory</field>
        <field name="view_type">form</field>
        <field name="view_mode">tree,form</field>
    </record>

    <record id="view_location_form" model="ir.ui.view">
        <field name="name">Location form - cycle count extension</field>
        <field name="model">stock.location</field>
        <field name="inherit_id" ref="stock.view_location_form"/>
        <field name="arch" type="xml">
            <xpath expr="//div[@name='button_box']" position="inside">
                <button string="Accuracy Stats" class="oe_stat_button"
                        icon="fa-line-chart" name="%(act_accuracy_stats)d"
                        type="action"/>
            </xpath>
            <field name="active" position="after">
                <field name="zero_confirmation_disabled"/>
                <field name="cycle_count_disabled"/>
                <label for="loc_accuracy"/>
                <div>
                    <field name="loc_accuracy" class="oe_inline"/> %
                </div>
            </field>
        </field>
    </record>

</odoo>