A third Element Class, Transient Elements

An Element or Cell can be made Transient and attach/placed or created in the DGN. The Transient Element can then be attached as a Reference, or as a DGN Library to another file.

Construction Elements are non-printing but are resident in the DGN, but a DGNLib with selected Transient Elements displayed but not resident would allow additional design content in the CAD file for the designer, but not distributed.

A DGNLib can be built with a range of Transient content like text, grids, point clouds, 2D, 3D, parametric or Rendering.

The Transient objects can also be copied from the DGNLib into the Active file and they become Primary Elements.

Alternatively, instead of, or being both, the option of attaching the Transient object file [which would be a missing attachment/or ignored when not available, or as a DGNLib which is silent when the file is distributed.