I have solved this question by myself.
Finally I found a great post with interesting topic.
Is it possible to turn off notifications from global chat ?
In the menu for the global chat, you should be able to mute the notifications for it specifically.
I dont see any option there, maybe its missing in Persona theme ? hmm
I think it stopped working in 1.13 - I remember it being there in 1.12 and there were no updates to that plugin for a long time.
I'm not sure if it wasn't a little bugged though - if I remember correctly the side effect of disabling notifications was that your chat window stopped updating global chat at all. You had to reload the tab (or possibly just reopen the popup window if that's what you used) to get new messages.