diff --git a/core/modules/config_translation/src/FormElement/FormElementBase.php b/core/modules/config_translation/src/FormElement/FormElementBase.php
index 7db01e1..19114ee 100644
--- a/core/modules/config_translation/src/FormElement/FormElementBase.php
+++ b/core/modules/config_translation/src/FormElement/FormElementBase.php
@@ -91,6 +91,9 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
    *   A render array for the source value.
    */
   protected function getSourceElement(LanguageInterface $source_language, $source_config) {
+    // @todo Should be able to render source as singular+plurals. Similar
+    // to TranslateEditForm::buildForm(), but here the source may also be
+    // multi-plural.
     if ($source_config) {
       $value = '<span lang="' . $source_language->getId() . '">' . nl2br($source_config) . '</span>';
     }
@@ -161,6 +164,8 @@ protected function getSourceElement(LanguageInterface $source_language, $source_
    */
   protected function getTranslationElement(LanguageInterface $translation_language, $source_config, $translation_config) {
     // Add basic properties that apply to all form elements.
+    // @todo Needs support for possibly singular+plurals input if the source
+    // was singular/plural. As in TranslateEditForm::buildForm().
     return array(
       '#title' => $this->t('!label <span class="visually-hidden">(!source_language)</span>', array(
         '!label' => $this->t($this->definition['label']),