I know that the NSW Office of Fair Trading (OFT) provides an on-line licence checking service for persons such as Strata Managers whose activities are covered by the Property, Stock and Business Agents Act 2002.
So maybe try that, and if substantiated complaints aren’t listed (as I know they are for tradespeople), then contact the OFT directly as I don’t see why general information about the numbers of complaints, and the numbers of those that have been substantiated / upheld could not be disclosed in the consumers’ interest.