I don’t think there’s a “professional” organisation of Strata Managers (eg like the Legal Practice Board or similar for lawyers) that you could complain to (possibly because the word “professional” is rarely seen in company with the words “strata manager”….?).
But surely your Strata Manager has a boss, if they are just one Manager in an agency? I’d start by calling the office and seeing if there is anyone “higher up”, and repeating what you have said here. It does seem unprofessional.
Otherwise, hold your head high, and simply tell anyone who cares to listen that you are simply concerned that things are done correctly, otherwise the cost consequences could be immense. Bringing up $$$ often makes people sit up and take notice.
Also, are you on the Committee? Can you get on the Committee? Surely someone with your knowledge should be there, not just barracking from the sidelines.