contract/contract_line_invoice_by_average/views/contract_line_view.xml

<odoo>

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

</odoo>