I realise I'm a bit late to the party. Good luck (tho I guess you've finished these ones now, in which case I hope they went well 🙂 ).
I always went low during exams, both at school and university, which is interesting because a typical stress response would be to go high (e.g. job interviews and the like) - I put it down to needing to concentrate hard for 2h+ 🙂
My exams were in the days before CGMs, so I'd test before the exam, always have food with me, and at the slightest feeling that I might be trending lower would eat something fast acting (often chocolate bars), there's nothing worse than not realising until you're actually low at which point you've got 10min+ of not being very useful in the exam, which is time I'd never get back.
There was no concept of extra time for hypos, it's an interesting though, I wonder how the schools police this though. I've not seen this applied at university either (though I've thankfully not had to invigilate an exams since before COVID)