I'd like my students to have 2 attempts at their quiz, but with different cutoff dates. If they miss the first deadline they lose their first attempt and so have only a single attempt remaining. But I still want the marking to be "take the highest mark".
I think the only way to do this is to make two copies of the quiz, with different cut-offs, and each one allowing only one attempt.
Then use a calculated column in the gradebook to combine the two scores.