title: How to implement a filter by shipping method in woocommerce backend?
body: <p>I need to implement a filter in the woocommerce backend, that I can use to filter the orders by the selected shipping method.</p>
  
  <p>I can create a filter on custom fields and alter the query, but the problem is that woocommerce stores the shipping method in a custom table of the DB.</p>
  
  <p>Any hints on how to achieve this filter?</p>