A Container App is submitted 1 time to Apple, adding internal or Outlet Apps does not require a re submission.  You simply add the Outlet App from your back office and as soon as you are completed it - the App is live inside the Container App.

The Only Time you would need to resubmit your App would be if new features are released and you want those new features in your app, or if you want to change the Icon, description or screen shots that are displayed in the App Store.