How do you override the add or edit node for a particular content type
Depending on where exactly you want to indicate that "away" status, I think you should rather alter the entity reference field widget for that specific field to add this "away" status rather than trying to achieve this via templates.

Sounds like you want to try implementing this hook:

function hook_field_widget_multivalue_WIDGET_TYPE_form_alter(array &amp;$elements, \Drupal\Core\Form\FormStateInterface $form_state, array $context) {
  // Add a css class to widget form elements for all fields of type mytype.
  $field_definition = $context['items']-&gt;getFieldDefinition();
  if ($field_definition-&gt;getType() == 'mytype') {
    // Be sure not to overwrite existing attributes.
    $elements['#attributes']['class'][] = 'myclass';
  }
}