Issue #2651228 by jordanpagewhite, webbykat: Add description beneath 'User the administration theme for editing content...' on the admin Appearance page

core/modules/node/node.module

@@ -832,6 +832,7 @@ function node_form_system_themes_admin_form_alter(&$form, FormStateInterface $fo
   $form['admin_theme']['use_admin_theme'] = array(
     '#type' => 'checkbox',
     '#title' => t('Use the administration theme when editing or creating content'),
+    '#description' => t('Control which roles can "View the administration theme" on the <a href=":permissions">Permissions page</a>.', array(':permissions' => '/admin/people/permissions')),
     '#default_value' => \Drupal::configFactory()->getEditable('node.settings')->get('use_admin_theme'),
   );
   $form['#submit'][] = 'node_form_system_themes_admin_form_submit';