Display text in an empty field group tab using custom code
Adding something like the below in hook_form_alter() works

&lt;?php
    $group_name = 'group_some_name';
    $form['test'] = array(
      '#type' =&gt; 'container',
      'content' =&gt; array(
        '#markup' =&gt; 'test',
        '#prefix' =&gt; '&lt;div&gt;',
        '#suffix' =&gt; '&lt;/div&gt;',
      ),
    );
    $form['#group_children']['test'] = $group_name;
    $form['#fieldgroups'][$group_name]-&gt;children[] = 'test';
?&gt;


Seems like I had to add wrap the content in '#type' =&gt; 'container' for it to work