Hi Allan,
in the computer/browser version there’s a link under each Challenge:
In the iOS app there’s a ballon-like (not sure how to call it, sorry!) on the top right of each challenge you can tap on to see the list.
Or you can find and download the whole list in a pdf in this thread:
https://forum.saysomethingin.com/t/vocabulary-from-challenges/
as long as you don’t read the next ones in advance, since both in the iOS and the downloadable files you can see them all!) 