In this article, I'll show you how to add Twig Template Suggestions for item list in drupal 8 with hook_theme_suggestions_item_list_alter():
/**
* Implements hook_theme_suggestions_item_list_alter() for form templates.
*
* @param array $suggestions
* @param array $variables
*/
function THEMENAME_theme_suggestions_item_list_alter(array &$suggestions, array $variables, $hook) {
if (isset($variables['element']['#id'])) {
$id = str_replace("-", "_", $variables['element']['#id']);
$suggestions[] = $hook . '__' . $id;
}
}
