You can move the widget outside of the group that is formatted to display narrow and on the right hand side.

Create your own ir.ui.view like this:

Be sure to choose the first  account.invoice.form view in the Inherited View field.

XML code:

<data>

<field name="outstanding_credits_debits_widget" position="replace"/>

<group class="oe_subtotal_footer oe_right" position="after">
  <group>
    <field name="outstanding_credits_debits_widget" colspan="2" 
           nolabel="1" widget="payment" 
           attrs="{'invisible': [('state', 'not in', 'open')]}"/>
  </group>
</group>

</data>

Your Invoices will now look something like this: