Implements hook_form_FORM_ID_alter().
Adds a button 'Save and add fields' to the 'Create content type' form.
field_ui_form_node_type_form_submit()
function field_ui_form_node_type_form_alter(&$form, $form_state) {
// We want to display the button only on add page.
if (empty($form['#node_type']->type)) {
$form['actions']['save_continue'] = array(
'#type' => 'submit',
'#value' => t('Save and add fields'),
'#weight' => 45,
);
$form['#submit'][] = 'field_ui_form_node_type_form_submit';
}
}