On the old activities page (http://connect.garmin.com/activities), after I filter, middle click opens the track in a new tab. This was awesome because I could search for old tracks of a certain length while trying to plan my next ride, then open a few in tabs to examine them.
In the modern one (http://connect.garmin.com/modern/activities), I can't open them in separate tabs. Middle click stays in the same tab, meaning a ton of back button nonsense. (On top of the slowness of that, when I hit the back button in the browser, the activities page goes back to its defaults. My filter is lost.)