[DanCooper]

There is an option in Settings => TV Shows => General => Media List Options => Display Missing Episodes to list known episodes that you don't have but already are listed on TVDb or TMDb. This episodes are grayed out in the list and flagged as "Missing" in the main window (see screenshot). Usually Ember get this information if you (re-)scrape a whole tv show. If you don't want to re-scrape the whole tv show and only get all "missing" episodes in your list you can use this function in the context menu. With this function none of your episodes or the tv show itself will be updated or changed.

If you add new episodes or a whole season you have to use the DB update function. Ember will add and scrape a new season automatically if needed like new episodes while a DB update.