There are many purchased modules where you have to create a game around it. You have to select the module and create game. However, many of these modules can be combined together, and these modules, such as Storm King's Thunder, even suggest combining them. However, you can't add just any module after the game is created. Some you can, but the large ones you can't. You have to create a new game and then transmogrify. This becomes incredibly painful to combine the large modules as these modules have hundreds of objects, contained within many many folders and sub folders. You have to select each object and drag/drop from within transmogrify and then recreate folders in target game and then drag drop each object into it's folder. Like I said, incredibly painful. Though I understand that there may be changes to transmogrify to allow copying folders and their contents, which would make combining significantly easier, the better approach is to treat ALL modules like add ons. So once game is created, go to add ons and magic, it's there. Want to add STK, go to Add Ons and add it. Roll20, you really want something like this. You want people to purchase more modules and integrate them quickly into their current campaigns. You don't want a painful process that you currently have.
