I have to add a button for printing delivery labels in the barcode scan page. (https://mydomain.com/barcode/web/#action=stock.ui&picking_type_id=7)

Usually inheritance is not a big deal, but on this particular page I don't get it.

In the stock module there is the stock.xml. In this file a webclient is generated where the widget.js loads a template in the picking.xml. (t t-name='PickingEditorWidget') 

I have to add the button with xpath in this picking.xml but I am not able to do that. Every method I know so far about inheritance in odoo doesn't work.

Does anyone have an idea how to achieve that?

Thanks in advance,

Thorsten

P.S.: odoo 8