I changed Amibench resolution to 1280x720 as this matches my Amiberry setup on Linux. Icons are a little bit big then, so I tried using the scaling option in "Amibench - Preferences - Icons - Sizes - Nominal Size: 80"
Scaling itself works (tough a few icons seem to disappear?), but I quickly found out that I can no longer click on icons on the Amibench desktop! They can no longer be clicked and also are not highlighted any longer when the mouse hovers over them. They can however be selected via area select. The then highlighted icon can be started via Amiga-O for Open - a nice workaround for no longer being able to click on them - and like this I was able to start the Preferences and change settings again.
After returning to standard 100% scaling everything was back to normal and I could click on the desktop icons again.
Firmware installed is 46.1.878, default AROS ROMs.