Maybe I wasn't clear enough (English is not my native language), I 'll try to explain it better.
Google Chrome can add a "button" to Windows bar but it can be considered a folder with a dedicated icon, with links to the Chrome Apps (Calendar, Gmail, Keep, Youtube, ecc) that in fact are just link to Google websites; I also added Mega extension for Chrome and it appeared in that place as well.
After installing Classic Shell that icon stopped working: the left clic does nothing and the right clic can only remove it or "open" it (but it does not open anything at all actually).
Update: after the 2nd reboot everything works fine and I did nothing at all...
Consider the issue solved!