On the Workspace menu, click on "Building Elements Sidebar" to add or remove it from the workspace. On the Elements sidebar, you will see the default building elements, as well as options called <default> and <null>. These elements cannot be deleted. When you create your own elements, they will automatically be added to this list. The software will auto-create new elements when it generates the analysis model. You will be able to double-click on a building element to open the Building Elements dialog.
Highlight a building element and use the Set Wall Element, Set Floor Element, and Set Ceiling Element tools to assign building elements to walls, floor surfaces, and ceilings. The Set tools can be used on both 2D and 3D views.
On the Elements sidebar, click on the down-arrow to open a context menu and select "Auto Hide" or "Hide".