This is a great idea! Archicad already has the OSD built in for undo/redo and various other tasks so it would make sense for this to happen.
Another case where this would be useful, I have up/down stories mapped to side scroll on my mouse for even faster jumping between stories. If someone else uses my computer (often during training) they can easily push the scroll wheel sideways by accident and jump a story with no idea of what just happened. The OSD would give a good visual cue as to what happened.
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