<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data>
    <record id="view_order_form_transaction" model="ir.ui.view">
      <field name="name">sale.order.form.transaction</field>
      <field name="model">sale.order</field>
      <field name="inherit_id" ref="sale.view_order_form"/>
      <field name="arch" type="xml">
        <field name="payment_term" position="after">
          <field name="transaction_id"/>
        </field>
      </field>
    </record>
  </data>
</openerp>

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data>
    <record id="view_order_form_transaction" model="ir.ui.view">
      <field name="name">sale.order.form.transaction</field>
      <field name="model">sale.order</field>
      <field name="inherit_id" ref="sale.view_order_form"/>
      <field name="arch" type="xml">
        <group name="sale_pay" position="inside">
          <field name="transaction_id"/>
        </group>
      </field>
    </record>
  </data>
</openerp>

Put the field transaction_id in the group 'sale_pay'
Put the field transaction_id in the group 'sale_pay'

Add the field inside the group instead of after a field.  In another module, I
add a button right after 'payment_term' and it must be right after it.  Adding
the field in the group prevent it to be placed between the payment_term field
and the button.
