Right now I have no idea of knowing if the verticle_tabs #default_tab actually works as describe.
Sadly there doesn't seem to be a test for testing this functionality. I have a feeling I'm doing something wrong which is why I can't for the life of me get the default_tab working but it might end up that this is just a bug.
Summary: Work has been done during sprint day on DrupalCon Amsterdam, adjusting paths since the structure of Drupal has changed the past 2 years.
Remaining tasks
- Remove whitespace from patch.
- Reroll patch.