Indeed, that could be an easier and quicker way to reproduce pieces of animations instead of copying keys.
What i do at the moment is during the set-up process, i create a animation track just to test the 3d effect of specific parts, as it's done in 3d softwares to test the rigging with "skin" or "physic".
So at anytime, i have a "backup" of my 3d effect in both direction with each controllers i've created.
I already done a video showing that, but it's about Zodiac episode 2 content... hope i'll be able to share it soon?!
On complex characters, it could be messy pretty quickly with all these bones/controllers, so i use the selection locker in the timeline but a actual option to sort keys might be very useful!
I know it's in the wish list on the trello board, but really looking forward for this kind of improvement to accelerate the process. Even more store selections with other keys please!!!