The Write STL File option allows you to write the STL file that is currently displayed in the 3D Viewer.
Shortcuts
Default Keys: None
Default Menu: 3D Design
Command: Write STL File
Locating this option
Available from: (3D Viewer) 3D Design menu > Write STL File option
Using the dialog
On selection, this will write everything currently displayed in the 3D Viewer to a file.