The "Imported modules" page appears in the settings notebooks of all program files (WPProgramFile class) and shows you the modules imported by the module.

The page only lists the modules which are explicitly imported. Neither dynamically loaded modules (loaded during program execution) nor indirect modules required by other modules are shown. (The former is usually impossible to determine statically, and the latter depends on the execution context -- things such as currently active LIBPATH, BEGINLIBPATH and ENDLIBPATH all determine which modules will be actually loaded.)

If you want to find out which module is really used by a given program file, you can use the PSTAT /L command while that specific program is running.