$ gn help toolchain_args
ERROR No help on "toolchain_args".
Run `gn help` for a list of available topics.


It'd be better if gn were to say `see gn help toolchain`, where toolchain_args is documented.

Ideas:

- Have an explicit list of "keyword", "where to look" pairs and manually curate this index (for things like toolchain_args in toolchain, bundle_partial_info_plist in tool -- but output_extension has its own entry already, etc).

- Have `gn help` look through the contents of each help section, and index all words listed on a line by themselves preceded by two spaces

- your idea here

The second option seems a bit better to me. Opinions?