My biscotti recipe says to refrigerate 30 minutes before the first baking. I want to refrigerate longer-like a day-so I can prep one day and

I agree - wrap it well and it should be fine.

One thought: I don't know if making/chilling dough a day ahead of baking is just a matter of time, but if not - unlike most cookies, that are best eaten the day they're baked, biscotti keep really well. In fact, I think they often get better after a couple of days. I've made them many times for parties or to send as gifts for that exact reason. (This may not be true for your recipe, but I've done it w/success for many variations of 'classic' biscotti - which are baked in a log, sliced, baked again.)

i cannot imagine how it would be a problem. As long it's well wrapped, so the dough doesn't dry out so much that it becomes too crumbly to slice cleanly, you should be fine. ;o)

I hope someone gives you an answer.
Prep, prep, prep a day or two before is my kind of cooking.