Multiple Tracking Boxes in Same Layer- How to remove/disengage a tracking box when tracking subject is no longer in frame?

Multiple Tracking Boxes in Same Layer- How to remove/disengage a tracking box when tracking subject is no longer in frame? I do not want to leave a tracking box that is no longer needed in the frame. Please advise. Thanks!

Either select the points and delete them or move them offscreen if you need to use the shape later in the shot.