When a new collection tree is added to Akonadi, where the root collection does not match current mime type filter, but it's children do match the filter, the collection tree is not displayed.

Let's have following tree of calendars/todo collections. When you create such tree and add it to Akonadi, it will not appear in the calendar list in KOrganizer. You have to restart KOrganizer to make them appear.

My Account  (Collection::collectionMimeType)
  |
  |------ My Calendar (KCal::Event::eventMimeType)
  |------ My Second Calendar (KCal::Event::eventMimeType)
  |------ My Tasklist (KCal::Todo::todoMimeType)


But if you create following tree (note the mimetypes in the root collection), the tree will appear in the calendar list immediately.

My Account  (Collection::collectionMimeType, KCal::Event::eventMimeType, KCal::Todo::todoMimeType)
  |
  |------ My Calendar (KCal::Event::eventMimeType)
  |------ My Second Calendar (KCal::Event::eventMimeType)
  |------ My Tasklist (KCal::Todo::todoMimeType)

Simply put, it looks like the filter does not check subtree of a newly added collection if the collection does not match the filter.