It sounds promising in theory and I agree that linking the Q/A cards to more detailed notes and tree structure is useful but in implementation it felt very clunky and I did not gel with the UI at all. The most immediate issue was that identifying how to actually markdown the notes into a usable question and answer format wasn't clear from the brief description in the intro document. The tool REALLY needs a tutorial. After I worked that out though the "learn" tab just felt like any other SR flashcard app and it didn't present the notes in any useful way to make it better than a well curated Anki deck.
I've never really tried anything except Anki, Memrise and now this app but it's just hard to recommend this over Anki, as a widely accepted and open source standard. I found this frustrating to use.