There is currently no legislation requiring a driver to wear or not to wear footwear whilst driving a motor vehicle in New South Wales.
However, if an accident was to occur and it was found that the cause of the accident was due to inappropriate or lack of footwear, an offence under Rule 297 of the Road Rules 2014 (driving without proper control of vehicle) could be applied.
Wearing high heel shoes / stilettos, heavy work boots, thongs, or any other footwear that could cause you to lose control of the vehicle is a bad idea. Generally speaking, you should choose a shoe that fits on the tight side, with good grip, but also comfortable and not too hot.