Extension to UpdateFormFields for Asset Folder not working anymore

Silverstripe 4.10.2

I’m trying to add a few fields to the Folder edit screen in the cms. The site previously had this feature, but I think it has stopped working at some point after an update. I can see old values in the DB for DisplayName. The DisplayName field is not showing in the admin though.

How can I fix this?

More generally, how do I see what has gone wrong here? is there a debug method to seeing what extensions are applied for example?

There is a similar post for Image assets, which I have tried to apply lessons from , but it is still not working. Perhaps different for Folders

    - 'DocumentFormFactoryExtension'

    - 'DocumentExtension'


use SilverStripe\ORM\DataExtension;

class DocumentExtension extends DataExtension
  private static $db = [
    'DisplayName' => 'Varchar',
    'Description' => 'HTMLText',
    'CustomOrder' => 'Int',

  public function ShowTitle($title){
    return  str_replace('-', ' ', $title);  



use SilverStripe\Core\Extension;
use SilverStripe\Forms\FieldList;

use SilverStripe\Forms\HTMLEditor\HTMLEditorField;
use SilverStripe\Forms\NumericField;
use SilverStripe\Forms\TextField;

class DocumentFormFactoryExtension extends Extension
  public function updateFormFields(FieldList $fields, $controller, $formName, $context)
      TextField::create('DisplayName', 'Display name')

   // I think these used to work before an update.  
    // $fields->addFieldToTab('Editor.Details', TextField::create('DisplayName', 'Display name'), 'Name');
    // $fields->addFieldToTab('Editor.Details', HTMLEditorField::create('Description', 'Description')->setEditorConfig('basic'));
    // $fields->addFieldToTab('Editor.Details', NumericField::create('CustomOrder', 'Custom order'));