Looks like you may have already found https://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines/Cycling_and_Foot_Paths#Closed/Illegal_Paths because you're tags are close.

What you have is pretty much it, except you got the key=tag a bit mixed up.

We write key=tag so left part is the key and right part is tag, it should be abandoned:highway=path not abandoned=highway=path as you have.

See also https://wiki.openstreetmap.org/wiki/Key:abandoned:highway