invoice_merge_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="view_invoice_merge" model="ir.ui.view">
        <field name="name">Merger Partner Invoice</field>
        <field name="model">invoice.merge</field>
        <field name="arch" type="xml">
            <form string="Merge Partner Invoice">
                <group>
                    <separator
                        string="Are you sure you want to merge these invoices?"
                        colspan="4"
                    />
                    <p>
                        Please note that:<br /><br />
                        Invoices will only be merged if:<br />
                        * Invoices are in state 'draft'.<br />
                        * Invoices belong to the same partner.<br />
                        * Invoices have the same company, partner, address,
                        currency, journal, salesman, account and type.<br /><br />
                        Lines will only be merged if:<br />
                        * Invoice lines are exactly the same except for the
                        product, quantity and unit.<br />
                    </p>
                </group>
                <group name="options">
                    <field name="keep_references" />
                    <field name="date_invoice" />
                </group>
                <footer>
                    <button
                        name="merge_invoices"
                        string="Merge Invoices"
                        type="object"
                        class="oe_highlight"
                    />
                    or
                    <button string="Cancel" class="oe_link" special="cancel" />
                </footer>
            </form>
        </field>
    </record>
    <record id="action_view_invoice_merge" model="ir.actions.act_window">
        <field name="name">Merge Partner Invoice</field>
        <field name="res_model">invoice.merge</field>
        <field name="binding_model_id" ref="model_account_move" />
        <field name="binding_view_types">list</field>
        <field name="target">new</field>
        <field name="view_id" ref="view_invoice_merge" />
    </record>
</odoo>