This is a bit odd,
the attached screendump is from NX7.5.5.4. and not customized at all.
What i did was RMB among the other icons - Assembly Navigator.
Then in my NX8.0.1.5 install, the corresponding RMB popup does not contain the line "Assembly Navigator" . ( as i can see.)
But, in the install directory under C:\siemens\nx8\UGII\menus\ there is a "ug_assembly_navigator.tbr"
that can be loaded and displayed.
Regards,
Tomas