Not sure what v. of OneNote you're using but in 2010 multi-level bulleted lists seem to be created automatically, just like in Word. If you type "1)", onenote sees it as the start of a list. If you then it enter and tab, you get a). Instead of ctrl+h+ai and +ao in Word, backspacing and tabbing indents or outdents the bullets.

Not sure if that's what you were looking for.