When I click on "add to reading challenge" on the book page and select a challenge, I can see the prompt descriptions, but not the notes.
There are a lot of challenges, especially themed challenges, where the creator will put the name/title of the prompt in the "description" field and the explanation or description in the "notes" field, here are some examples:
https://app.thestorygraph.com/reading_challenges/661aaef9-5b58-46d5-935e-934e8d2057ee
https://app.thestorygraph.com/reading_challenges/15d26056-a6e8-478c-80be-e2a37c5729cc

What I do right now is:
go to "add to reading challenge" --> click on challenge --> open prompt in new tab via "see prompt page" link --> go to new tab --> click on title of challenge --> browse challenge to find the prompt that fits --> go back to previous tab --> choose prompt, save book to challenge

Maybe most people don't match a book to challenge prompts after reading it, but I wish this were easier, because I don't want to click on every "see prompt page" link in a challenge until I find one that fits.