When I say a series within a series, I'm thinking specifically television though it could be used elsewhere like novels and movies. And I'm specifically asking for a "series" of shows that fall under one umbrella but don't encompass the whole franchise. In a specific hypothetical, I'm looking for a word that would be used for several different tv shows that are all related to a specific topic and exist within the same cinematic universe, but are apart from other tv shows in the same cinematic universe.

Examples that aren't quite what I'm looking for but related: A movie example would be the Star Trek reboot movies. That series of movies are called the "Kelvin" movies for in-universe reasons. But they don't encompass the whole franchise. There are other movies and TV shows within the Star Trek franchise.

A more specific movie example could be the Captain America movies. There's 4 movies in the Captain America series of films, but there's more movies in the overall series of films known as the Infinity Saga. And the Infinity Saga does not encompass the entire Marvel franchise.

A TV example even if it doesn't fit the criteria well, would be in Season 1 of Star Trek: Discovery the Season was broken up into 2 different "Chapters" The first Chapter consisted of 9 episodes and was all about the Klingon war and the second chapter consisted of 6 episodes and was about the mirror universe. Most people would call this series of episodes within a series of seasons within a TV series, an "arc." I'm not looking for the word arc, which is why I said the Star Trek Discovery example did not fit the criteria well. It's just to give you a ball-park of what I'm looking for.

Maybe there isn't a word. But if there is, I'd like to know it. Also if you can find any words that are tangential that could also be helpful.