vracoop_api_v2/views/pos_transaction_views.xml

<odoo>
    
    <record id="pos_transaction_form_view_api" model="ir.ui.view">
        <field name="name">pos.transaction.form</field>
        <field name="model">pos.transaction</field>
        <field name="inherit_id" ref="vracoop_pos_free_balance_v2.pos_transaction_form_view"/>
        <field name="arch" type="xml">
            <xpath expr="//sheet" position="before">
                <header >
                    <button string="Send Mayam" type="object" name="send_to_mayam" />
                </header>
            </xpath>
            <field name="date_iso" position="after">
              <field name="transaction_send"/>
            </field>
        </field>
    </record>

</odoo>