Under Spanish there's a "Words" tab where it has all the vocab you've learned so you can go through it like flip cards. Any word on when Swahili will be getting that? I find this vocab much harder to remember and it'd be convenient to have on here, rather than making my own and trying to track all the words I've come across myself.
Languages that came out of the incubator don't get a word tab, I think. It's only first courses that Duo made and maintain themselves.
They are not perfect and are not straight from the source, but there are TinyCards decks with Kiswahili vocabulary based on their individual lessons. I find them very useful to retain difficult words than using DuoLingo only. They have enabled me to continue to take new lessons without fear of advancing too far ahead without the earlier vocabulary to back me up.