J’ai modifie le le fichier :
/etc/xdg/menus/lxqt-applications.menu
de maniere a ne pas toucher aux fichiers .desktop
regrouper le menu original dans une seule categorie
copier des categories existantes et les modifier avec la balise “Not”
Creer une categorie Mise a Jour avec uniquement 3 lanceurs avec la balise “Filename” (comme la categorie screensaver qui elle fonctionne)
Modifier la partie “Layout” pour que les categories “MenuOriginal” et “Miseajour” soient bien separees du reste
Est ce que quelqu’un saurait me dire comment faire les deux dernieres modifs ?

Le fichier modifie qui fonctionne presque comme je veux :
<Name>Applications</Name>
<Directory>lxde-menu-applications.directory</Directory>
<!-- Read standard .directory and .desktop file locations -->
<DefaultAppDirs/>
<DefaultDirectoryDirs/>
<!-- Read in overrides and child menus from applications-merged/ -->
<DefaultMergeDirs/>
<!-- Dans cette partie je conserve les categories qui conviennent et exclue les applications non souhaitees-->
<!-- Accessories -->
<Menu>
<Name>Accessories</Name>
<Directory>lxde-utility.directory</Directory>
<Include>
<And>
<Category>Utility</Category>
<!-- Accessibility spec must have either the Utility or Settings
category, and we display an accessibility submenu already for
the ones that do not have Settings, so don't display accessibility
applications here -->
<Not><Category>Accessibility</Category></Not>
<Not><Category>System</Category></Not>
<!-- Les applications que je ne souhaite pas dans la rubrique accessoires -->
<Not><Filename>qtpass.desktop</Filename></Not>
<Not><Filename>info.desktop</Filename></Not>
<Not><Filename>compton.desktop</Filename></Not>
<Not><Filename>vim.desktop</Filename></Not>
</And>
</Include>
</Menu> <!-- End Accessories -->
<!-- Accessibility submenu -->
<!-- End Accessibility -->
<!-- Development Tools -->
<!-- End Development Tools -->
<!-- Education -->
<Menu>
<Name>Education</Name>
<Directory>lxde-education.directory</Directory>
<Include>
<And>
<Category>Education</Category>
<!-- Les applications qui sont deja dans la categorie Office ne doivent pas apparaitre ici -->
<Not><Category>Office</Category></Not>
</And>
</Include>
</Menu> <!-- End Education -->
<!-- Games -->
<Menu>
<Name>Games</Name>
<Directory>lxde-game.directory</Directory>
<Include>
<And>
<Category>Game</Category>
</And>
</Include>
</Menu> <!-- End Games -->
<!-- Graphics -->
<Menu>
<Name>Graphics</Name>
<Directory>lxde-graphics.directory</Directory>
<Include>
<And>
<Category>Graphics</Category>
<Not><Category>Utility</Category></Not>
</And>
</Include>
</Menu> <!-- End Graphics -->
<!-- Internet -->
<Menu>
<Name>Internet</Name>
<Directory>lxde-network.directory</Directory>
<Include>
<And>
<Category>Network</Category>
<!-- Les applications que je ne souhaite pas dans la rubrique internet -->
<Not><Filename>org.kde.bluedevilsendfile.desktop</Filename></Not>
<Not><Filename>org.kde.bluedevilwizard.desktop</Filename></Not>
</And>
</Include>
</Menu> <!-- End Internet -->
<!-- LXQt-About -->
<!-- End LXQt-About -->
<!-- Multimedia -->
<Menu>
<Name>Multimedia</Name>
<Directory>lxde-audio-video.directory</Directory>
<Include>
<And>
<Category>AudioVideo</Category>
</And>
</Include>
</Menu> <!-- End Multimedia -->
<!-- Office -->
<Menu>
<Name>Office</Name>
<Directory>lxde-office.directory</Directory>
<Include>
<And>
<Category>Office</Category>
</And>
</Include>
</Menu> <!-- End Office -->
<!-- System Tools-->
<!-- End System Tools -->
<!-- Other -->
<!-- End Other -->
<!-- Settings -->
<!-- End Settings -->
<!-- Leave -->
<Menu>
<Name>X-Leave</Name>
<Directory>lxqt-leave.directory</Directory>
<Include>
<And>
<Category>X-Leave</Category>
</And>
</Include>
</Menu> <!-- End Leave -->
<!-- Screensaver -->
<Menu>
<Name>Screensaver</Name>
<Include>
<Filename>lxqt-lockscreen.desktop</Filename>
</Include>
</Menu> <!-- End Screensaver -->
<!-- CATEGORIE POUR MISE A JOUR ET INSTALLATION NOUVEAUX LOGICIELS -->
<Menu>
<Name>Z MISE A JOUR</Name>
<Directory>z-miseajour.directory</Directory>
<Include>
<Filename>upg-apply.desktop</Filename>
<Filename>org.kde.discover.desktop</Filename>
<Filename>org.kde.muon.desktop</Filename>
</Include>
</Menu> <!-- End Z Mise a jour -->
<!-- CATEGORIE QUI REGROUPE LE MENU ORIGINAL LXQT -- INDENTATION AUGMENTEE DE 2 POUR PLACER LA NOUVELLE CATEGORIE ZZZ ADMIN -->
<!-- RIEN D AUTRE DE MODIFIER ICI -->
<Menu>
<Name>ZZZ ADMIN</Name>
<Directory>zzz-admin-lxqt-original.directory</Directory>
<!-- Accessories submenu -->
<Menu>
<Name>Accessories</Name>
<Directory>lxde-utility.directory</Directory>
<Include>
<And>
<Category>Utility</Category>
<!-- Accessibility spec must have either the Utility or Settings
category, and we display an accessibility submenu already for
the ones that do not have Settings, so don't display accessibility
applications here -->
<Not><Category>Accessibility</Category></Not>
<Not><Category>System</Category></Not>
</And>
</Include>
</Menu> <!-- End Accessories -->
<!-- Accessibility submenu -->
<Menu>
<Name>Universal Access</Name>
<Directory>lxde-utility-accessibility.directory</Directory>
<Include>
<And>
<Category>Accessibility</Category>
<Not><Category>Settings</Category></Not>
</And>
</Include>
</Menu> <!-- End Accessibility -->
<!-- Development Tools -->
<Menu>
<Name>Development</Name>
<Directory>lxde-development.directory</Directory>
<Include>
<And>
<Category>Development</Category>
</And>
<Filename>emacs.desktop</Filename>
</Include>
</Menu> <!-- End Development Tools -->
<!-- Education -->
<Menu>
<Name>Education</Name>
<Directory>lxde-education.directory</Directory>
<Include>
<And>
<Category>Education</Category>
</And>
</Include>
</Menu> <!-- End Education -->
<!-- Games -->
<Menu>
<Name>Games</Name>
<Directory>lxde-game.directory</Directory>
<Include>
<And>
<Category>Game</Category>
</And>
</Include>
</Menu> <!-- End Games -->
<!-- Graphics -->
<Menu>
<Name>Graphics</Name>
<Directory>lxde-graphics.directory</Directory>
<Include>
<And>
<Category>Graphics</Category>
<Not><Category>Utility</Category></Not>
</And>
</Include>
</Menu> <!-- End Graphics -->
<!-- Internet -->
<Menu>
<Name>Internet</Name>
<Directory>lxde-network.directory</Directory>
<Include>
<And>
<Category>Network</Category>
</And>
</Include>
</Menu> <!-- End Internet -->
<!-- LXQt-About -->
<Menu>
<Name>LXQt-About</Name>
<Include>
<Filename>lxqt-about.desktop</Filename>
</Include>
</Menu> <!-- End LXQt-About -->
<!-- Multimedia -->
<Menu>
<Name>Multimedia</Name>
<Directory>lxde-audio-video.directory</Directory>
<Include>
<And>
<Category>AudioVideo</Category>
</And>
</Include>
</Menu> <!-- End Multimedia -->
<!-- Office -->
<Menu>
<Name>Office</Name>
<Directory>lxde-office.directory</Directory>
<Include>
<And>
<Category>Office</Category>
</And>
</Include>
</Menu> <!-- End Office -->
<!-- System Tools-->
<Menu>
<Name>System</Name>
<Directory>lxde-system-tools.directory</Directory>
<Include>
<And>
<Category>System</Category>
<Not><Category>Settings</Category></Not>
<Not><Category>PackageManager</Category></Not>
<Not><Category>X-Leave</Category></Not>
<Not><Category>Screensaver</Category></Not>
<Not><Filename>lxqt-about.desktop</Filename></Not>
</And>
</Include>
</Menu> <!-- End System Tools -->
<!-- Other -->
<Menu>
<Name>Other</Name>
<Directory>lxde-other.directory</Directory>
<OnlyUnallocated/>
<Include>
<And>
<Not><Category>Core</Category></Not>
<Not><Category>Settings</Category></Not>
<Not><Category>Screensaver</Category></Not>
</And>
</Include>
</Menu> <!-- End Other -->
<!-- Settings -->
<Menu>
<Name>DesktopSettings</Name>
<Directory>lxde-settings.directory</Directory>
<Menu>
<Name>LXQtSettings</Name>
<Directory>lxqt-settings.directory</Directory>
<Include>
<And>
<Category>LXQt</Category>
<Or>
<Category>Settings</Category>
<Category>PackageManager</Category>
</Or>
</And>
<!-- Include some optional components here -->
<Filename>obconf-qt.desktop</Filename>
<Filename>compton-conf.desktop</Filename>
<Filename>pcmanfm-qt-desktop-pref.desktop</Filename>
</Include>
<Layout>
<Filename>lxqt-config.desktop</Filename>
<Separator/>
<Merge type="menus"/>
<Merge type="files"/>
</Layout>
</Menu>
<OnlyUnallocated/>
<Include>
<Or>
<Category>Settings</Category>
<Category>PackageManager</Category>
</Or>
</Include>
<Exclude>
<Or>
<Filename>lxqt-config.desktop</Filename>
</Or>
</Exclude>
<Layout>
<Merge type="menus"/>
<Merge type="files"/>
</Layout>
</Menu> <!-- End Settings -->
<!-- Leave -->
<Menu>
<Name>X-Leave</Name>
<Directory>lxqt-leave.directory</Directory>
<Include>
<And>
<Category>X-Leave</Category>
</And>
</Include>
</Menu> <!-- End Leave -->
<!-- Screensaver -->
<Menu>
<Name>Screensaver</Name>
<Include>
<Filename>lxqt-lockscreen.desktop</Filename>
</Include>
</Menu> <!-- End Screensaver -->
<Layout>
<Merge type="files"/>
<Merge type="menus"/>
<Separator/>
<Menuname>DesktopSettings</Menuname>
<Menuname show_empty="false" inline="true">LXQt-About</Menuname>
<Separator/>
<Menuname show_empty="false">X-Leave</Menuname>
<Menuname show_empty="false" inline="true">Screensaver</Menuname>
</Layout>
</Menu> <!-- End ZZZ ADMIN-->
<Layout>
<Merge type="files"/>
<Merge type="menus"/>
<Separator/>
<Menuname show_empty="false">Z MISE A JOUR</Menuname>
<Separator/>
<Menuname show_empty="false">ZZZ ADMIN</Menuname>
<Separator/>
<Menuname show_empty="false">X-Leave</Menuname>
<Menuname show_empty="false" inline="true">Screensaver</Menuname>
</Layout>