In the context of translating the Python documentation to french (https://github.com/AFPy/python_doc_fr), I did not found a way in the sphinx documentation (did I missed it ?) to provide a way for the readers to change the language of a currently displayed part of the doc (probably by jumping on the same part of the doc on a completely different directory, for clarity / maintenability / SEO / whatever).

Also, the "link" should probably be generated / displayed / clickable only if the target translation is completed, to avoid misleading users and bots.

The check about the completeness of a translation should probably be computed per rst file and not per po files as sometimes po files can be huge (Python documentation library.po is ~24k msgid, covering like 300 rst files.).

I'm not on the design / user interface / ux side so I can't think of something user friendly, but someone probably does ? :-)