nm-applet se trouve effectivement dans ../autostart
$ ls /etc/xdg/autostart/
abrt-applet.desktop gnome-settings-daemon-helper.desktop pulseaudio.desktop
at-spi-registryd.desktop gnome-user-share.desktop pulseaudio-kde.desktop
bluetooth-applet.desktop gnome-volume-control-applet.desktop restorecond.desktop
gdu-notification-daemon.desktop gpk-update-icon.desktop seahorse-daemon.desktop
gnome-at-session.desktop imsettings-start.desktop sealertauto.desktop
gnome-keyring-daemon.desktop krb5-auth-dialog.desktop user-dirs-update-gtk.desktop
gnome-power-manager.desktop nm-applet.desktop vino-server.desktop
gnome-screensaver.desktop polkit-gnome-authentication-agent-1.desktop xscreensaver-autostart.desktop
gnome-settings-daemon.desktop print-applet.desktop
Mais je suppose que si je le vire, il démarrera plus si je lance une session Gnome... Or je désirerais conserver les deux environnements, et que nm-applet démarre sous gnome et knetworkmanager sous KDE...