Here's a trick you can use in the interim until this capability can be added. Just change the end date of the game session to encompass the date when you reveal the additional bits of content. Once you modify the end date, those newly revealed snippets now appear within the last game session.
Technically, the last game session could run all the way until the night before the next game session if you want. As long as the START time is accurate, the end date really doesn't matter all that much. And you can easily note the TRUE end date within the session notes if you want to track that detail.