In Blender 2.8, we made the Timeline simpler by moving many options into popovers.
However, there are a few advanced features that some users would like to be able to see at a glance without opening up the popover to check.
We can support this by adding these items to the Timeline Sidebar, which is currently empty.
The main options where this is relevant is the Keying Set option, as well as the New Keyframes setting.
With this solution, the Timeline can remain simple and uncluttered, but with added complexity if users open the Sidebar.