Point taken on the tooltip. I think `isPicker` *is* a hack. There is enough special-casing of the 2 sidebars that they should probably be separate templates (and views). Some examples:

- different tooltips on draggable elements
- potentially different desired drag behavior
- different styling (text and color) on the vertical bar
- different click behavior (ToC view does not need to also open a book in the ToC view)