What I actually want to do: I've installed chromium-browser and I want to change the launch command from "chromium-browser" to "chromium-browser --proxy-server=http://localhost:8008"

Every application installs a .desktop file in /usr/share/applications that specifies application settings (name, comment, exec command, icon, menu, etc). Edit the chromium desktop file located at /usr/share/applications/chromium-browser.desktop and change the Exec= line to read:

Exec=/usr/bin/chromium-browser --proxy-server=http://localhost:8008 %U

What I actually want to do: I've installed chromium-browser and I want to change the launch command from "chromium-browser" to "chromium-browser --proxy-server=http://localhost:8008" .

I have looked through the instructions at http://wiki.xfce.org/howto/customize-menu and a lot of them don't seem to work (directories that don't exist for me) or do what I want to do.

I have tried using LXMenuEditor, as that page suggests - and it has *some* menu entries I wanted to remove show up (e.g. I removed gnumeric and it left the menu entry behind, but I could delete it with LXMenuEditor), but the menu entry for chromium-browser just doesn't appear in it.

I have no problem with editing config files, but I need to know where they are ...

When an app is installed in Ubuntu and the installer adds a menu entry ... where does this menu entry live, as far as Xfce is concerned?

(And do I have to edit it for the whole system, or will editing only for me do the job?)