You can safely include upto the post of "manager".
However, if you need anything more than that... say professional occupations such as "Doctor, lawyer, Engineer" ... the submitting passport documents must include your copy of the degree certificate as well.
It's always good to have this field filled with correct details of your employment as it will help you later when applying for VISA's or PR's !
This can be later changed by re-submitting relevant documents and amending the passport. They will NOT issue a new passport but "type" the new profession on the next page !