How to redirect from confirmation page back to page of form?
I have written the code for d7 where the article node form once submitted it is redirected back to the form.
    It will help you for d8.
    /**
     * Defines hook_form_alter()
     */
    function demo_form_alter(&amp;$form, $form_state, $form_id) {
        if (strstr($form_id, 'article_node_form')) {
          $form['actions']['submit']['#submit'] = array('demo_form_submit');
        }
    }
    // custom submit handler for '_node_form'
    function demo_form_submit($form, &amp;$form_state) {
      // call default action
      node_form_submit($form, $form_state);
      $form_state['redirect'] = url('node/' . 'add' . '/article', array(
          'absolute' =&gt; TRUE
        )
      );

      $_GET['destination'] = $form_state['redirect'];
    }