Hi Nicolas, the manual would enjoy a subsection in "Hacking" on how to create a new exporter, either from scratch or as a derived exporter. (Such a subsection can be short enough, thanks to derived backend.)
>From this section, we can throw links to the exporter reference document and the Org syntax document published on Worgs. We may also add footnotes referring to the Org syntax relevant sections, when needed. But both reference documents don't fit into the manual IMO. They are great resources for developers, not for users. The footnotes are enough for advanced users who want to go beyond the manual. Thanks! -- Bastien