FB Plus Challenge: Reschedule?

When the March challenge came out, I didn't want to reschedule my current program, so I scheduled the challenge for the future - no problem. But now other things have come up, and I would love to move it around in my calendar.

But I can't find the reschedule option!

Is it somewhere unexpected that I haven't spotted?

Or if not, would it be possible to get a reschedule function for the monthly challenges, please?

(In this case, I'll do some more shuffling and complete it roughly when it's currently scheduled, but it would be handy to have in future. I reschedule a LOT!)