You’ll notice an “Add notes” button within the word/phrase editor:
This allows you to add a free-text note. This note will then be available within practice sessions. Any words/phrase with a note attached will have a “Show note” button which you can click to see the note. It’s hidden at first just in case you don’t want to see a potential clue before you’ve had a chance to think about that challenge or flashcard.
If you find this feature useful, I’d love for you to share exactly how you’re using it!