It would be awesome if I could search the sentences where I gave an incorrect response multiple times. (10+ times, 5+ times etc). This combined with % mastered filter could create a powerful search tool for sentences to troubleshoot. There are some words/expressions that are particularly tricky for me to remember, and I am adding them to a collection currently, but that doesn’t let me distinguish the different levels of difficulty for me. As more and more sentences become available for review, being able to target those unrelenting sentences without having to manually manage them via collection / favorite would be really useful. I noticed that when I am reviewing a round history after a review session, it enables me to search for sentences for which I’ve answered incorrectly more than once. So I am hoping this is a viable feature in a broader use.