To edit the ceiling, first click on the ceiling to open the properties panel on the left.

Click Edit Shape in the lefthand panel. Once in the Sketcher mode, sketch in the changes you intend to make to the shape, and click on Apply to save changes.

Enter the desired value into the Thickness field.

Enter the desired value into the Elevation field.

Go to the Material menu in the panel, click on the drop-down menu to select a user-defined material, or select Fetch from Store to open a carousel of various other materials. Select the desired material by clicking on it.

Click on the Delete Ceiling option in the left panel.