What's the point of a .desktop file with NoDisplay=true
You can create an icon that launch an application in background.
Details from Desktop Entry Specification:
NoDisplaymeans "this application exists, but don't display it in the menus". This can be useful to e.g. associate this application with MIME types, so that it gets launched from a file manager (or other apps), without having a menu entry for it (there are tons of good reasons for this, including e.g. thenetscape -remote, orkfmclient openURLkind of stuff).