Similarly to the link type, you can now add one more link directly in the form using the more_link type. You can provide an optional #title attribute to control the text of the link. If no #title attribute is provided, it will default to More. Consider the following example:

$form['more_link'] = array( 
  '#type' => 'more_link', 
  '#title' => $this->t('See more'), 
  '#url' => new Url('<front>'), 
);