Our sisters sites on the coast have an option under Additional Information within the requested sighting information to record for the Yellow-tailed Black Cockatoo via photographs of chewed sapling stems. Haven't felt the need to do this for our region but it is a possible option.
The damage is pretty conclusively YTBCs, because Bardi-grub seekers would use a tomahawk, which would leave a different-looking scar. Good point though Ryl, it could be yesterday’s damage, last week’s or last month’s!