The Designer functionality for interactive visual creation of reports, print templates etc. is an integrated part of the List & Label component and therefore will become part of your application. The Designer is not a standalone application, but it will be programmatically launched from your application. This is typically implemented within an event handler triggered by a menu item. The Designer will show up as a modal pop-up window overlapping your application window.
You can pass on this designing capability to your end users so that they can define individual templates or adapt the templates offered by you to personal requirements.