Passing form value into batch process
You can pass variables to the batch process by doing the following...

     $year = "2018";
     $batch = array(
          'title' =&gt; t('Bulk Add happening within the Bulk Add Form file...'),
          'operations' =&gt; array(
            array(
              '\Drupal\create_perf_plan_for_new_year\BulkAddNode::bulkAdd',
              array($uids, $year)
            ),
          ),
          'finished' =&gt; '\Drupal\create_perf_plan_for_new_year\BulkAddNode::bulkAddFinishedCallback',
        );


Year in this case can obviously be anything... a piece of $form_state for instance also works.

You could then change 

public static function bulkAdd($uids, $year, &amp;$context){
    $message = 'Bulk add happening in functional file...';
    foreach ($uids as $uid) {
        $user = \Drupal\user\Entity\User::load($uid);
        \Drupal\node\Entity\Node::create([
            'type' =&gt; 'perf_plan',
            'title' =&gt; 'Perf-plan-' . $year . '-' . $user-&gt;get('field_user_employeeid')-&gt;value,
            'uid' =&gt; $user-&gt;id(),
            'field_employee_uid' =&gt; $user-&gt;id(),
            //'field_supervisor_uid' =&gt; $user-&gt;get('field_supervisor')-&gt;first()-&gt;getValue()['target_id'], //Brilliant means of getting entity reference UID from User. SM
            //'field_director_uid' =&gt; $user-&gt;get('field_director')-&gt;first()-&gt;getValue()['target_id'],
          ])-&gt;save();
    }
    $context['message'] = $message;
  }


Hope this helps. It took me a while to figure out where in the batch array structure this needed to be placed. I didn't find the docs particularly helpful.