I propose a new duolingo feature- create your own lessons and skills for private use.
I was thinking it would be very useful that once you finish your tree and you start looking to expand your vocabulary beyond the course, you can learn and test yourself on these new words right here by translating sentences that you wrote yourself or found somewhere else. we could also add our own hints and tips.
Isn't DuoLingo heavily designed around their Incubator http://incubator.duolingo.com?
When I read e.g the Czech Incubator status updates it is clear, it takes it's time for someone to jump in and learn how to use it...otherwise the Czech course main contributor would have added more....
DuoLingo sentences and words are pretty hardwired.
You can NOT even jump to a specific (locked/grey) skill, just because words are used fixed from the skills before (even you may not have learned it).
I tried direct skill jumping with some grammar skills in the old Python portal.....and I failed because of unknown vocabulary.
I don't think that you will see any feature like this in the near future.....or DuoLingo would require a technical redesign.
DuoLingo is NOT about one word - one sentence (like Memrise, Mondly), but a bunch of sentences per word and alternative answers accepted.
But it would be very nice seeing (e.g paying) "upper-intermediate / advanced" course material added by the DuoLingo company, staff and contributors.
Yes, I like that too!
Because Duolingo's teaching method is very good for people, who are more interested in science than in learning languages.
For those people, I would like to design and create a course "English Chemical Safety Words and Sentences for Dutch speakers" and the reverse tree.
Other teaching methods are very boring for them (like TinyCards, Memrise and former language classes at school)