Is there a single shortcut to create a new artboard in Illustrator? If not how could I set one up?
You can set up keyboard shortcuts in Illustrator through Edit > Keyboard Shortcuts. At least on Win, it's possibly in Illustrator on Mac; the shortcut is Alt+Shift+Ctrl/ Cmd+K.
If a certain action is not in that list, it's very well possible you can't create a shortcut for it at all. I suspect that to create a new artboard, you'd have to enter location and size, and Illustrator can't make anything without you entering those. In that case, you might want to make an action out of it and assign a shortcut to that action.