How to use tokens in webforms? I'm trying to use the [current-page:url] token in a webform hidden field (as the default value) but the submission shows "[current-page:url]" literally. 
Am I missing something?
token is a contributed module and not part of Drupal 8 or webform installation.  You have to install and enable before you can use it. 

composer require drupal/token
drush en token


NOTE: Webform is not aware of token directly and does not complain because it thinks are you just inputting text