Launcher icon docked in panel gets duplicated when clicked

[sblanzio]

Hello!
Usually, in my LM21 when I add an existing application to the taskbar panel, the icon works both as a launcher and an aggregator for all the instances (windows) of the same application. If the application is running the launcher icon becomes active (underlined) and I can preview the window hovering that same icon... I think you get the idea, it is the expected behavior.

Now, I had to install Firefox Developer Edition, but that is not available via repositories. So I followed this tutorial https://tecadmin.net/install-firefox-de ... on-ubuntu/ to have that installed.

This worked, but then I couldn't find the app con in the applications menu. So, since I also wished to have my Firefox Developer Edition docked to my panel, followed this tutorial https://kerneltips.com/add-applications ... ux-mint-20.

This worked too. Now I can find the app in the menu and I have the launcher docked in the launch panel, but the problem is when I click my launcher Icon on the panel, another duplicated icon gets created and while this last one behaves as expected it is an unwanted duplicate and it disappears when the app is closed. I tried to make it permanent rightclicking and choosing "Create shortcut", but it just won't stay.

How do I make my launcher icon in the panel, from my manually installed app, work as all of the other launcher icons in the panel?
Thank you very much for your help