pos/pos_invoice_journal/views/pos_config.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2016 Alex Comba - Agile Business Group
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl). -->

<openerp>
<data>

    <record model="ir.ui.view" id="pos_config_form_view">
        <field name="name">pos.config.form (in pos_invoice_journal)</field>
        <field name="model">pos.config</field>
        <field name="inherit_id" ref="point_of_sale.view_pos_config_form"/>
        <field name="arch" type="xml">
            <xpath expr="//field[@name='journal_id']" position="after">
                <field name="invoice_journal_id" widget="selection"/>
            </xpath>
        </field>
    </record>

</data>
</openerp>