Collapsed and collapsible Field Sets in Admin I have created a fieldset (which groups a field collection). Because it has a few nested levels and many fields, I want it to be shown collapsed. I am trying this code but it does not work. The id is retrieved directly from the source code of the web browser. The fieldset is the top-level, and there are more fieldsets inside of it. The form is displayed in the Admin page, the node edit form. The field "field-seo-general" is a #container.

function hook_form_alter(&amp;$form, &amp;$form_state, $form_id){
    if($form_id == "my_form"){
        $form["field-seo-general"]['options']['attributes']["#collapsible"] = TRUE;
        $form["field-seo-general"]['options']['attributes']["#collapsed"] = TRUE;
      ...
} // function
I have solved it installing the module Field Collection Fieldset, and instead of Embedding the Field Collection, I have put it as a Fieldset, and then one of the options is to be shown Collapsed at rendering. All with a module.