I’ll let others give their more comprehensive thoughts, but my understanding is that yes you can get engaged. However, you’ll have to wait until you get divorced BEFORE you get married again. (The Marriage Act states that bigamy is illegal in Australia.) So it sounds like you'll be wanting to get your divorce finalised as soon as possible - sounds like you have a few months longer to go as you will need to satisfy the Family Court that you and your ex have lived separately and apart for at least 12 months. The Family Law Courts website takes you through what you need to do and has some good information in simple language.
Worldly1 is right, you are able to get engaged, you just won't be able to marry until you have finalised your divorce.
The Family Law Courts of Australia states the following on their website:
I have applied for a divorce, is it safe to set a wedding date for my new marriage?
You should not plan to remarry until the divorce order is finalised. In most cases, this is one month and one day after the divorce hearing, however, you should not assume the divorce will be granted at the first court hearing. For example, you may be told at the hearing that you need to provide more information.
If you intend to remarry, you must give the marriage celebrant a Notice of Intended Marriage at least one month before the wedding date, and comply with other requirements of the Marriage Act 1961.
As soon as the divorce order is granted, the marriage celebrant may accept the Notice of Intended Marriage. You must show a copy of the divorce order to the marriage celebrant before the wedding can take place.