1st shortcus in the n900 are located in the following folder:
/usr/share/applications/hildon

view folder via your web browser:
file:///usr/share/applications/hildon

next you can either edit the existent shortcut or make a copy and edit the copy...

to edit files i found the following method the easiest:
i installed midnight commander:
http://my-maemo.com/software/applica...42&fldAuto=949
and run mc from the x-terminal
(root is fine otherwise system files appear locked when saving changes):
sudo gainroot
mc

from mc you also can enter cmd's like you do in the x-terminal.
please note where the cursor is flashing in the mc lower area.

for example type or paste the following:
cd /usr/share/applications/hildon
(this changes the location of the folder you want to view in the mc pane)
tip: you can paste from the clipboard to mc - in the n900 top drop down menu (mc app) and select past, ctrl+v does not work in mc.

then simply use the cursor keys to find/navigate to the file...
then to edit file in mc tap the menu at the bottom (4-edit)

the line you would need to change and add the parameter will be something like the following example:

exec=/path_to_app/app
change to
exec=/path_to_app/app -MyNewParameter

save changes to file from the menu at the bottom (tap the save option)

try to start your application again (normal way you start your app) and it should now take the new parameter.

that's it!

Thanks for the guide!

I've tried to add a parameter to the osso-xterm, but it seemed not to work. For anyone else facing this issue, delete this line from the osso-xterm.desktop file:

X-Osso-Service=xterm

The wiki article describes what was going on there:

X-Osso-Service (string, DBus service name) - if specified hildon desktop will try to call the top_application method on this service rather than execute what is listed in the Exec field).