I appreciate the option to sort flashcards on the web version of the site, will this feature eventually come to the app as well? My biggest peeve is not having a summary of vocabulary memory strength either overall or post-review. I have specific words I keep forgetting and I wish the site would flag those or give me the option to flag them manually. That way I can revisit the lessons that feature those words. For now I've just been taking a screenshot (when I remember) of the words I keep forgetting to review later.

I think the website uses SRS (Spaced repetition system) so the ones you keep forgetting should show up more frequently on it's own anyways, if you told the program you forgot them. Otherwise you could use Anki which gets recommended a lot. I personally use Pleco with the SRS module and I'm very happy with it...