server-ux/base_cancel_confirm/templates/cancel_confirm_template.xml

<?xml version="1.0" encoding="UTF-8" ?>
<flectra>
    <template id="cancel_reason_template">
        <div>
            <group
                colspan="4"
                t-attf-attrs="{'invisible': [('cancel_reason', '=', False)]}"
            >
                <field name="cancel_confirm" invisible="1" />
                <field name="cancel_reason" readonly="1" />
            </group>
        </div>
    </template>
</flectra>