Drupal Webform missing edit link for fields from CiviCRM database
Version incompatibility introduced in Webform version 7.x-4.12 and webform civicrm 7.x-4.13.

Upgrade webform civicrm to 7.x-4.14 solves problem.

Drupal issue https://www.drupal.org/node/2600878 details this.