Bálint Junkuncz
--- a/modules/custom_elements_ui/src/Form/EntityCustomElementsDisplayEditForm.php
+++ b/modules/custom_elements_ui/src/Form/EntityCustomElementsDisplayEditForm.php
      '#size' => 20,
      '#required' => TRUE,
    ];
-    return parent::buildForm($form, $form_state);
+
+    $form = parent::form($form, $form_state);
+
+    // Remove "extra fields".
+    foreach ($form['fields'] as $key => $field) {