I tried your suggestion, but it does not work. It appears that chained tokens are not working with the Webform module yet. I say yet because they are currently working on (https://www.drupal.org/node/2873307) tokens for sub-elements, when you have a composite field with several sub-fields in it. I have filed an (https://www.drupal.org/node/2877360) issue regarding chained tokens.
I tried your suggestion, but it does not work. It appears that chained tokens are not working with the Webform module yet. I say yet because they are currently working on (https://www.drupal.org/node/2873307) tokens for sub-elements, when you have a composite field with several sub-fields in it. I have filed an (https://www.drupal.org/node/2877360) issue regarding chained tokens.