I think the best model to visualising how hidden transactions would work is actually to think of it as 2 views, “Important Transactions” vs “All transactions”. Like “Pinned” vs “All” in inbox by Gmail.
If you’re worried about hidden transactions being missed, or people assuming incorrect maths, you could summarise groups of hidden transactions, “8 Hidden Transactions: -£58.37”.
Perhaps the word “Hidden” is the sticking point. How about Junk, Unimportant, Boring, ect.