The cornice object creates an object in the floor-floor ceiling by default, with a selected profile. View Object from the toolbar Plasterboard click the icon.
Fundamental Based and Align Above Floor modes in the toolbar are automatically active.
At the same time, the profiles to be used in the plasterboard object are listed in the Section box.
If desired, a different profile can be selected from the Section box.
Mouse over the tile and left click.
Cornice will form under the flooring.
If desired, one of the free drawing and path based drawing modes can be selected.