The sidebar component directs the opening of the notebook. This is for two reasons:

* it's a little bit easier to save the UI state of the current sidebar
  (immediately before the notebook is opened), in case in the future we
  want to restored it.

* to avoid adding additional events, like `show/hideSidebarControls`,
  that probably would be needed for granular control of the sidebar, in
  case the notebook would be directing the process of closing/re-opening
  the sidebar.