Whether you consider it an advantage or a disadvantage standard configuration dialogs in GNOME tend to be a bit limited and because of that do not allow all kinds of behavior customizations that one may desire to do. It is done that way in order to maximize ease of use and user friendliness.
For deeper configurations there is gconf-editor (
apt-get install gconf-editor |
in Debian/Ubuntu).
By default, GNOME’s dialog for running applications is gnome-run which is brought up with an Alt-F2 keyboard shortcut. You can change this to something else. In this example we will change it to gmrun, a very simple and lightweight, but quite powerful dialog for running commands (features tab completion, unlike standard gnome-run).
- Open gconf-editor
- Go to apps > panel > global and change a run_key line by deleting
<Alt>F2as its value (this disables the old run command functionality) - Now go to apps > metacity > global_keybindings and change the run_command_1 to
<Alt>F2 - Then go to apps > metacity > keybinding_commands and change command_1 to gmrun (or other program that you may prefer for this purpose).
In global_keybindings shortcuts are set by numbers (1 in this case) and in keybinding_commands the command numbered with a corresponding number will be launched. So in this case, when you press Alt-F2 gmrun will launch. And that’s what we wanted. 
Cheers