One thing I've found in my testing is that if you have a lot of events and scenes in a period, the actual period itself can scroll off the top of the screen. While this isn't really a big deal, having the period pinned to the top of the list would be much nicer than having it go scrolling off with the rest of the events and scenes.
I mocked up a small demonstration by duplicating the div holding both the period title card and the event list, then left the period title in the first and the event list in the second. It looks exactly like what I would like to see.
Show GIF demonstration

