trytond-product_cost_plan/view/cost_plan_product_line_tree_external_party.xml

<?xml version="1.0"?>
<!-- The COPYRIGHT file at the top level of this repository contains the full
     copyright notices and license terms. -->
<data>
    <xpath expr="/tree/field[@name='uom']" position="after">
        <field name="party_stock"/>
    </xpath>
</data>