Parent keyframes to markers
A way to parent multiple keyframes to layer markers would be fantastic. For example, having several animations that use multiple properties with different start points across a number of layers, it becomes laborious to adjust all of the timings quickly. Moving a layer marker and adjusting all of the keyframes, while keeping the timing the same between them, would be very handy! The plugin Animation Composer from MrHorse has this functionality already, but you can only do it with the set animations within the plugin.
steve marth commented
I can't vote on this idea enough! Too bad I can only vote once. This is the single change to After Effects that would make the most positive difference in my daily work, and would substantially speed up and simplify just about every project I work on. It would also relieve so many headaches when handing files off to a different animator.
It seems like such a simple addition; I know making these new features on Adobe's back end is probably more complicated than I can understand, but all you're doing is making the frame number at which a keyframe is placed equal to the frame number of a marker on the timeline.
Adobe! Please! Do this one for me!