Yael from WorldNomads.com here.
If you have already purchased a World Nomads policy, you are unable to add additional destinations to your Certificate of Insurance, however I would recommend contacting our Customer Service team: https://pp.worldnomads.com/contact-us, as they can check your specific policy to see if you already have coverage to Australia included.
If you haven't yet purchased a policy, then you are certainly able to include all the countries you are planning to visit, simply type each one into the Quote calculator to receive the price.
Happy travels! 6 months ago