Actually if you just have to add one field, I find it way less complicated to just edit the original xml files. For instance, if you want to add the reference field to the list view of the sale orders: just edit sale_view.xml under the sale module (Openerp/server/server/openerp/addons/sale) and add your field.

Example:

            <tree string="Sales Orders" fonts="bold:message_unread==True" colors="grey:state=='cancel';blue:state in ('waiting_date','manual');red:state in ('invoice_except','shipping_except')">
                <field name="message_unread" invisible="1"/>
                <field name="name" string="Order Number"/>
                <field name="date_order"/>
                <field name="partner_id"/>
                <field name="user_id"/>
                <field name="client_order_ref"/>
                <field name="amount_total" sum="Total Tax Included"/>
                <field name="state"/>
            </tree>
        </field>
    </record>

    <record id="view_quotation_tree" model="ir.ui.view">
        <field name="name">sale.order.tree</field>
        <field name="model">sale.order</field>
        <field name="priority">4</field>
        <field name="arch" type="xml">
            <tree string="Quotation" fonts="bold:message_unread==True" colors="grey:state=='cancel';blue:state in ('waiting_date','manual');red:state in ('invoice_except','shipping_except')">
                <field name="message_unread" invisible="1"/>
                <field name="name" string="Quotation Number"/>
                <field name="date_order"/>
                <field name="partner_id"/>
                <field name="user_id"/>
                <field name="client_order_ref"/>
                <field name="amount_total" sum="Total Tax Included"/>
                <field name="state"/>

If you take this approach for the list view, adding "<field name="client_order_ref"/>" in between the existing fields will be sufficient. No other parameters have to be adjusted.