I might be totally missing something but is it not possible to add css classes to properly style the "Show More" button using an existing framework like it is with item / empty / root?
Thanks for the feedback @mindbits, it is indeed a problem with our API. We should add a way to provide a custom CSS class to the button.
Most helpful comment
Thanks for the feedback @mindbits, it is indeed a problem with our API. We should add a way to provide a custom CSS class to the button.