When you select marks (point marks, curve marks etc.) in photographs, the “Expand Selection to all Windows” tool moves the selection to all marks associated with the same underlying Object on all open photos and the Object in the 3D Viewer(s) and Table(s). When you select Object Points in the 3D Viewer or Point Table this menu item will select all associated Marked Points on all open photographs. The same applies to edges, Bent Tubes, cylinders, curves, and silhouettes. See also Sub-selection Highlighting.