stock_picking_views.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="view_picking_withcarrier_out_form" model="ir.ui.view">
        <field name="model">stock.picking</field>
        <field name="inherit_id" ref="delivery.view_picking_withcarrier_out_form" />
        <field name="groups_id" eval="[(4, ref('base.group_no_one'))]" />
        <field name="arch" type="xml">
            <xpath expr="//header" position='inside'>
                <button
                    name="schenker_get_label"
                    string="Schenker Label"
                    type="object"
                    attrs="{
                        'invisible':[
                            '|',
                            '|',
                            ('delivery_type', '!=', 'schenker'),
                            ('carrier_tracking_ref', '=', False),
                            ('state', '!=', 'done')
                        ]
                    }"
                />
            </xpath>
        </field>
    </record>
</odoo>