contract/contract_line_invoice_by_average/views/contract_line_view.xml

<odoo>

    <record id='contract_line_form_view' model='ir.ui.view'>
        <field name='name'>inherit.contract.line.form.view</field>
        <field name='model'>contract.line</field>
        <field name='inherit_id' ref="contract.contract_line_form_view"/>
        <field name='arch' type='xml'>
            <field name='price_unit' position='after'>
                <field name='products_invoiced_by_avg_ids' widget="many2many_tags"/>
            </field>
        </field>
    </record>

</odoo>