Starting from build 7269 CtrlShiftF7 on implements/extends allows to see the methods implemented/extended (http://www.jetbrains.net/confluence/display/IDEADEV/EAP7269Release+Notes).
That's nice but in a big files one has to go and look for highlights all the way down. When I've tried to CtrlAltF7 the implements/extends it said "Cannot search for usages". What if it could ? I mean, what if CtrlAltF7 pressed on implements/extends would display a pop-up with the list of methods implemented/extended ? Possibly with an option to click and navigate to them (like in Ctrl+F12) ?