Hello, Texinfo allows one to create new named indices using `@defindex NAME`, which can then be used via `@NAMEindex`. I have been experimenting with different ways of supporting this.
I have learned how to add an option `TEXINFO_ADDITIONAL_INDEXES` that can be used to create multiple uses of `@defindex` in `org-texinfo-template`. That part is straight forward. Currently, the Texinfo export uses pre-supported keywords, such as `#+FINDEX` for `@findex`. However, in my testing, the index names are case sensitive, while keywords are converted to upper case when parsed. I have tested recognizing keywords matching the form ".*INDEX" in `org-texinfo-keyword`, but it requires converting lower case to upper case (or vice versa), which might be unexpected. After thinking about it, I wonder whether it would be better to have a dual-valued keyword like `#+INDEX[name]: text`, which would avoid needing to convert between letter cases and restricting users. However, it looks like secondary values are restricted to keywords affiliated with other Org structures. In my testing, it looks like `org-element-keyword-parser` includes the dual value as part of the key name. Would it be possible to allow un-affiliated keywords to also have dual values? I have CC'd the e-mail address listed in `ox-texinfo.el`, in case they have any thoughts on this. Thank you.
