extract manpage table of content

ZSHMISC(1)                   General Commands Manual                  ZSHMISC(1)
NAME
       zshmisc - everything and then some
SIMPLE COMMANDS & PIPELINES
       A simple command is a sequence of optional parameter assignments followed
       ...
PRECOMMAND MODIFIERS
       A simple command may be preceded by a precommand modifier, which will
       ...

I would like the extract a Table of Content from manual page such as below

SIMPLE COMMANDS & PIPELINES
PRECOMMAND MODIFIERS

1. :redir @a - setup redirect to register a
2. :g/^\u.*/p - find all lines start with upper case and print them
3. :redir END - end the redirection
4. "ap - paste content in register a