How can I add an icon on the taskbar for a running application without icon? [duplicate]
Solution 1:
I have solved the issue, thanks to this answer
I had just to add the following line to .desktop file of the application:
StartupWMClass=XXXXX
Where XXXXX is the name of the application in lower case without quotes, obtained by running xprop WM_CLASS on the terminal and clicking on the application window.