In a recent 1-3 boxed set promo, I saw why boxed set series "series" is not a bad idea. I had minimal co-sales with other books

after selling hundreds in an international BookBub. I'm finding that "related series" on Amazon is such a loose connection for readers that few are buying other books on Amazon during boxed set sales. They are, but it's minimal. And, I'm wondering if it might be worth it to just throw ALL the individual books, even prequel, into ONE single series. 1st prequel as book 1, for example.
So... I'd love your opinions because I haven't made up my mind yet. I have 10 books and 2 boxed sets in the series.
1) For my
boxed sets, I'm thinking of making boxed set collection series. It'd be 2 books on Amazon. That way if I advertise the boxed set, the other one (books 3-6) is a click away from an also bought
2) For my witch series
individual books in general, I'm thinking of taking my "related books" and throwing them in ONE bundle. In other words, prequel as book 1, prequel short story as book 2, Book 1, Book2 etc. "Artistically" this still works because every book, including short stories, carries on while the other left off. I've hesitated in doing this in the past because I use my initial novel as a lead-in. But now I'm wondering if I it won't hurt my sales to still advertise that book? This is a tough decision. It could mean increasing sales of the novellas and short stories while dropping sales overall without a good 1st book lead-in.
As an aside, to show the power of Amazon's one click series link, I had a whole slew of preorder sales for my upcoming xmas witch story as co-sales with my Halloween promo. Why? Because I decided to tag it, for now, as Book 7 in the series. It's not a lie. The book is a continuous story chronologically. Point is, it tells you how important series distinctions are.
{note this mostly involves Amazon algos, not other retailers