The user should be able to flip objects horizontally and vertically in the layout view with a hotkey. This already exists in tilemap view so it'd quite convenient to have in the regular layout view. This is a pretty common feature across editors as well.
These are the hotkeys currently being used for tile editing, which could be applied here as well:
X Flip horizontal
Y Flip vertical
Z Rotate 90 degrees clockwise
A Rotate 90 degrees anti-clockwise