Select and label timeline elements to move them together in time
I spend too much time hunting and pecking for which timeline elements are associated with corresponding movement in the viewport. Shifting layers, in/out points, and keyframes in time often takes multiple selection passes. And there's no way to store that selection, so they each have to be selected every time they need to be adjusted (and in/out points can't even be selected so they all need to be done separately... every time!).
Selectable in/out points and labels/groups for ALL timeline elements--any combination of keyframes, markers, in/out points, and layers--would strengthen the visual connection between the timeline and the viewport AND allow for faster timeline adjustment of those grouped movements.