Turn on Twig Debug Mode in Drupal 8 on Pantheon
When working on Drupal 8 theming, it is very helpful to have Twig debug mode on. Debug mode will cause twig to emit a lot of interesting information about which template generated each part of the page. The instructions for enabling debug mode can be found within the comments of the default.services.yml file, among other sources. In short, all you need is the following in your services.yml file:
parameters: twig.config: