Oh I see. To my knowledge those 3 large buttons are GTK-specific (and so specific to jami-gnome). As I understand it, jami-qt acts like any other regular program’s window, leaving window decorations such as the title bar and its buttons to the window manager to figure out. I could try looking into making left-clicking the tray icon close the window, but that could get confusing, because on some desktop environments there is no distinction between left-clicking and right-clicking the icon (and right-clicking the icon currently brings up a menu with a Quit option). Perhaps we could add a ‘Close’ option to that menu but I’m not sure how useful that would be.
Alternatively, I would suggest looking into awesome-wm’s configurations to see if it allows customizing how it makes title bars look.
Hope this helps!