This is currently only about the Gnome menu and I hope that a KDE user will post a solution for the KDE version soon.
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For Gnome:[/size]
1. Browse to “/usr/share/applications” and check which shortcuts you wish to remove.
2. Open up a terminal window (Start Menu > Gnome Terminal) and type: “sudo rm /usr/share/applications/X” and press enter (where X is the filename of the menu item.)
*
For example:*
sudo rm /usr/share/applications/gedit.desktop
Note: You can also partially type a name and press TAB to make it autocomplete if only one result is found
For example:
sudo rm /usr/share/applications/gedit > TAB > sudo rm /usr/share/applications/gedit.desktop
Enjoy!