targets:
  dev:
    resources:
      jobs:
        Workflow1:
          email_notifications: {}
          webhook_notifications: {}
  stage:
    resources:
      jobs:
        Workflow1:
          email_notifications:
            on_success:
              - me@myorg.com
            on_failure:
              - me@myorg.com
          webhook_notifications:
            on_failure:
              - id: stg_id
  prod:
    resources:
      jobs:
        Workflow1:
          email_notifications:
            on_success:
              - me@myorg.com
            on_failure:
              - me@myorg.com
          webhook_notifications:
            on_failure:
              - id: prod_id

So I would have to push the resource into the target keys to add environment variance. That makes sense. If I get this to work, I will post again. 

Thanks!