I\'m using Prestashop 1.6.0.9.
I wish to edit the raw HTML for this part.
The filters for BO orders are created by controllers\admin\AdminOrdersController.php.
In order to preserve prestashop core code it's indicated you create an override for this controller, where you'll need to join the table that you need (if not already joined), specify where in your table is the field you want to use for filter and also the field itself. Have a closer look at the constructor function of AdminOrdersController to better understand how to do this.
For example if you want to add the carrier name as a filter, create override\controllers\admin\AdminOrdersController.php file and add the following code:
_join .= 'LEFT JOIN `'._DB_PREFIX_.'carrier` cr ON (cr.`id_carrier` = a.`id_carrier`)';
$this->_select .= ', cr.name as carrier';
$this->fields_list['carrier'] = array(
'title' => $this->l('Carrier'),
'align' => 'text-center'
);
}
}