In this article, I'll show you how to add Twig Template Suggestions for block Elements in drupal 8 with hook_theme_suggestions_block_alter():
/**
* Implements hook__suggestions_HOOK_alter().
*/
function THEMENAME_theme_suggestions_block_alter(array &$suggestions, array $variables)
{
if (!empty($variables['elements']['#id'])) {
$block = Drupal\block\Entity\Block::load($variables['elements']['#id']);
$suggestions[] = 'block__' . $block->getRegion();
$suggestions[] = 'block__' . $block->getRegion() . '__' . $variables['elements']['#id'];
} elseif (!empty($element['content']['#block_content'])) {
$block_bundle = $element['content']['#block_content']->bundle();
$suggestions[] = 'block__' . $block_bundle;
}
return $suggestions;
}
