The scroll bar of System Tray of Status and Notifications can't be scrolled using mouse middle button or touchpad scroll instead you have to drag the scroll bar and move it each time which annoying a lot. Reproducible: Always
System tray icons can also react to mouse wheel events, such as the volume or battery icon, and this would conflict with scrolling. I agree it's not optimal but there's no way both input events could be handled without conflicting. Note that you can also drag the entire view (like on a phone) rather than just the scroll bar.
that can do, thanks