The question of what KPIs should my employee have is similar to asking what lead / lag indicators (KPIs) should my company use. Using a generic set of KPIs developed by others runs the risk of measuring things which don't actually provide any actionable feedback - if you see your LTIFR / TRIFR go up all you know is your company (possibly) needs to "be more safer".
What is detailed in the Position Description for your H&S Coordinator? What are their expectations or responsibilities, and what skills do they need to have (or develop)? Once you identify these you can set down KPIs related to their responsibilities / expectations / required skills, with consideration that the KPI should also be able to provide feedback on what needs to be changed/adjusted return to the desired outcomes if there is current a deviation from them.
So I would first ask - why are we hiring a H&S Coordinator, and what is the work we need the to do?
Also to consider is what the H&S Coordinator can reasonable contribute to the success of the overall KPIs of the company - so if the company has a KPI to "Improved levels of worker participation and engagement with H&S", while it would be unfair to pin this all on the H&S Coordinator you could consider that a reasonable KPI for them could be "feedback on the how it was to deal with the H&S Coordinator from a sample of the workforce is normally Positive/constructive".