Form submission handler for the 'Save and manage fields' button.
field_ui_form_node_type_form_alter()
function field_ui_form_node_type_form_submit($form, &$form_state) {
if ($form_state['triggering_element']['#parents'][0] === 'save_continue') {
$admin_path = Drupal::entityManager()
->getAdminPath('node', $form_state['values']['type']);
$form_state['redirect'] = "{$admin_path}/fields";
}
}