What is the macro/code or whatever that shows the tree of a file, i.e.
an outline of the file showing all its section headings, chapter
headings, etc in a separate buffer above your working buffer, and is
called by "C-=". I did use it very successfully, but I overwrote its key
sequence but now want to re-associate it and use it again. Can you help
please?

Thanks
Sharon.
-- 
A taste of linux = http://www.sharons.org.uk
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Debian 8.0, fluxbox 1.3.7, emacs 24.5.50.2