Saving 3D Constructions / Catalog
When a 3D construction is selected it can be saved in the catalog over the context menu opened with a right mouse click.
All 3D constructions, including those provided with the software and the examples shown previously, are saved in the construction elements catalog 
(directory \AEC\Solids). If required, you can create in the normal way your own sub-directories to save new 3D constructions. The files of 3D constructions have their own file format *.solids. The directory in the catalog is called ‘Solids’, as is the folder in the preview. As with 3D objects, 3D constructions can be easily inserted and positioned when planning using drag and drop
More:
Visibility of 3D Constructions and Subtraction Solids
2D Representation of 3D Constructions
Materials of 3D Constructions
What to use – 3D Objects or 3D Constructions?