Drupal - Save for Later using Workbench, conditional required fields
Yes, this should be fairly easy to do with hook_form_&lt;form-id&gt;_alter():

&lt;?php

function MODULENAME_form_page_node_form_alter(&amp;$form, &amp;$form_state) {   
  $target_field = "FIELDNAME";
  $workbench_state_required = "draft";

  $form[$target_field]['#states'] = array(
    'required' =&gt; array(
      ':input[name="workbench_moderation_state_new"]' =&gt; array(
        '!value' =&gt; $workbench_state_required
      ),
    )
  );
}


Just replace MODULENAME with the name of your custom module, and FIELDNAME with the field in question to toggle required or not (you can print the $form array in this function to work out the exact field name if you like).

For more information on the Form States API, visit: api.drupal.org.