Suggestion: tag words as difficult
It would be nice if you could tag words on Duolingo which are difficult to memorize, or those which one thinks are going to be difficult. Then one could either check or strengthen his list of difficult words. For example, I was just introduced to a new word in german ("Verpflichtungen"), and I am pretty sure I am going to forget its meaning a lot of times.
I have seen this issue suggested a number of times...I think the thing is that Duo's algorithm already does this for you when you get a word wrong...but I agree that it would be really nice to be able to customize it. There could even be a section on your home page for practicing ONLY words you've marked as difficult?...it does seem like it would be more effective than just relying on the algorithm.
There are a number of reasons for getting a word wrong though. I get words wrong all the time simply because of typos or misreading the sentence. So according to Duo's algorithms I find those words more difficult than I actually do.
I'd like to see the ability to flag words as high priority so they move to the top of the review queue quicker. These words could either be words I'm struggling to remember, or words that I find important towards my goals. For example, someone might be travelling soon, so being able to say "Where is the airport" is pretty important to them. They should be able to tag words like Airport, Taxi, and Bus Stop and have those words take priority in the lessons.
Oh this would be very useful. I still trip up over l'asciugamano (Italian; the towel).
By the way, my Mom warns that Legal German (contracts, lawsuits, etc.) is a whole different kettle of fish even from High German. So best of luck with that.