Go use https://github.com/BlenderBoi/timeline-buttons instead. Archiving so I can make a separate addon to only add the framerate slider.
Addon for blender which adds various buttons from timeline into the dopesheet on the right-hand side.
Includes framerate, frame start/end, auto keying, and a current frame slider.
Sadly it does show in the normal timeline too making the timeline a bit more hefty because they seem to be the same window somehow, on the bright side they won't push buttons away and just go off screen if you need to shrink that window.
Limitation from blender. Though now that these buttons are in the dope sheet, I don't know what the point of using the timeline is. It just seems to be the dope sheet without colored channels.
