Hi Mike
There are no defined criteria for notifiable incidents. WorkSafe is yet to release a fact sheet similar to the one for injuries.
They know we need one, in construction we are having this debate , especially for falling stuff, made worse by clients having a more risk averse interpretation not supported by the legislation .
All I can advise is that you make u some examples that suit your industry and emphasise 'serious risk' and 'immediate exposure'.

A word of caution Phil - The Worksafe 'notify now' tool has a serious flaw which they have acknowledged.
It does not allow you to state that there was immediate exposure to serious risk of e.g. electric shock. Instead it skips that essential portion of section 24. I have just tried again and it tells me that it is not notifiable when I say no to electric shock, but yes to risk of , yes to powered equipment but no to anyone hurt.
So caution around the online tools- often not vetted by inspectors who know the ingredients of the act.