<edit> Deleted mistyped answer

Hi all, my problem was that in form referred there was create="false".

Deleting create="false" it works.

Anyone know if is possible have "add an item" with m2m fields?

HI! You must enter 

<page name="purchase_lines" string="Products">
    <field name="order_line"/>
    <tree create="0">
        <field name=""/>
        <field name=""/>
    </tree>
</page

Hi,

don't make things difficult, you can simply disable the add an item on one2many fields my making read-only or

define a view under One2many field and make the add  attribute under each view as " create='false' "

eg:

1.

<page name="purchase_lines" string="Products">
    <field name="order_line"/>
</page>
2.
<page name="purchase_lines" string="Products">
    <field name="order_line">
        <tree create="false">
            ....
            ....
        </tree>
        <form create="false" edit="false">
            ....
            ...
        </form>
    </field>
</page>

All examples hides add_an_item on One2many field.

Hi,

The add an item button comes when you add a one2many field in the view.

There is no need to do any work in the js file.

If you want to add same page like products then add it in <notebook> tag not in <page>.