I'm writing a modul, now I can add a field like this:
<record id="sale_order_form_ext_view" model="ir.ui.view">
<field name="name">sale.order.form.ext</field>
<field name="model">sale.order</field>
<field name="type">form</field>
<field name="inherit_id" ref="sale.view_order_form" />
<field name="arch" type="xml">
<xpath expr="//field[@name='carrier_id']" position="before">
<field string="Liefertermin" name="delivery_date" placeholder="Liefertermin"/>
<field string="Lieferung" name="delivery" placeholder="Lieferung" />
</xpath>
</field>
</record>
But when I want to put it under the order_policy, it doesn't work :
<record id="sale_order_form_ext_view" model="ir.ui.view">
<field name="name">sale.order.form.ext</field>
<field name="model">sale.order</field>
<field name="type">form</field>
<field name="inherit_id" ref="sale.view_order_form" />
<field name="arch" type="xml">
<xpath expr="//field[@name='order_policy']" position="before">
<field string="Liefertermin" name="delivery_date" placeholder="Liefertermin"/>
<field string="Lieferung" name="delivery" placeholder="Lieferung" />
</xpath>
</field>
</record>
Why is that so difficult? The field order_policy is at "other information" but on the same sale_order