There were quite a few of these plants (c. 50 or more) growing in the wheel ruts in which water has colected, on a track adjacent to the northermost access to the eastern shoreline of Lake Ginninderra, just south of the North Lawson Defence land. I'm fairly sure of the ID, but will be happy to be corrected.
Here's the PlantNet entry: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Atriplex~prostrata
There are records from eight ACT locations of this species in the Atlas of Living Australia, most around Lake Burley Griffin and a 2009 record by Rosemary Purdie in Latham by Ginninderra Creek. A 2005 WWF report in which Richard Grooves was the lead author considers this plant to be a significant environmental weed in that it is a problem in at least four seperate locations. It seems to like ares of high salinity - but is capable of becoming abundant in non-saline areas. Rainer, given its location near the Lawson grasslands would you be able to pull and bag plants - happy to help you in this task. Michael