This extension adds a small button in the main toolbar, which enables to collect all running headers in the notebook and display them in a floating window. The table of contents is automatically updated when modifications occur in the notebook. The toc window can be moved and resized, the table of contents can be collapsed or the window can be completely hidden. The position, dimensions, and states (that is 'collapsed' and 'hidden' states) are remembered (actually stored in the notebook's metadata) and restored on the next session. The floating window also provides two links in its header for further functionalities:

the "n" link toggles automatic numerotation of all header lines
the "t" link toggles a toc cell in the notebook, which contains the actual table of contents, possibly with the numerotation of the different sections.

The state of these two toggles is memorized and restored on reload.

Configuration

The initial configuration can be given using the IPython-contrib nbextensions facility. The maximum depth of headers to display on toc can be precised there (with a default of 4), as well as the state of the toc cell (default: false, ie not present) and the numbering of headers (true by default). The differents states and position of the floating window have reasonable defaults and can be modfied per notebook).

Limitation

Due to restrictions in the current notebook format, recurrent headlines cannot be distinguished and the ToC will link to the first occurrence.

Testing

At loading of the notebook, configuration and initial rendering of the table of contents were fired on the event "notebook_loaded.Notebook". Curiously, it happened that this event was either not always fired or detected. Thus I rely here on a combination of "notebook_loaded.Notebook" and "kernel_ready.Kernel" instead. Because of that, I propose to not overwrite the original toc and I put the extension in "testing" to avoid any possible/unknown side effect, though it works nicely for me.
This also includes a quick workaround as described in https://github.com/ipython-contrib/IPython-notebook-extensions/issues/429

History

This extension was adapted by minrk https://github.com/minrk/ipython_extensions from https://gist.github.com/magican/5574556
Added to the ipython-contrib/IPython-notebook-extensions repo by @JanSchulz
Modified by @junasch (automatic update on markdown rendering),
@JanSchulz, (enable maths in headers links)
@jfbercher december 06, 2015 -- (automatic numbering, toc cell, window dragging, configuration parameters)
@jfbercher december 24, 2015 -- nested numbering in toc-window, following the fix by @paulovn in @minrk's repo. December 30-31, updated config in toc2.yaml to enable choosing the initial visible state of toc_window via a checkbox ; and now resizable.