The Imported Objects section of the Visibility on Photos pane controls whether 3D imported points (and point id's), 3D imported lines, and 3D imported surfaces are visible on open photographs. See Importing and Setting Up Coordinate Systems.
After an Imported Object has been added and its 3D position calculated (by marking control, pinning or as a static) it's 3D visibility can be turned on and the imported object will be projected onto the photos.
The Imported objects section will only appear on this pane if at least one import has been added to the project.
Note: 3D items are displayed on oriented photographs only. See the section on Photo Projections for more information.