How to change command behind an icon in the launch bar?

[Bao_Niu]

Currently I have an icon sitting in my launch bar, with corresponding command:
Dia

I want to change the launching command to:
LIBOVERLAY_SCROLLBAR=0 dia

and preserve the icon.
so each time when I click on the same icon it will launch Dia with the new command.
Is it possible to do this? And how? Many thanks.

[deadflowr]

If it's a regular application you can:
first open gedit.
Then, for ease of use, open the file manager and then
go to the folder /usr/share/applications
Find the application, and then drag it into the gedit window.
Edit the command line "Exec="

At this point, I also add something like My in front of the program name
"Name=My Program"
Then open the file menu option and go to save as(not save)
And save the file in /home/username/.local/share/applications.

Then open the dash and search for the program.
When found, add it to the launcher and it should stay there, regardless of what happens from then on.

[Bucky Ball]

Right click launch bar>Add New Item>Launcher>set up your launcher with a name, an icon pic if you want one, and command.

Test it. Delete the old icon with 'dia' as the command.

[mc4man]

Locate the .desktop associated with Dia, open in a text editor, (root if in below address). Find the Exec= line & edit to -

Exec=env LIBOVERLAY_SCROLLBAR=0 dia %F
May need to log out/in to affect in launcher

Likely will be found in /usr/share/applications/dia.desktop