Check your URL, so that you enter the https://fr.numista.com site. If you just typ "numista" in the URL field and press enter, you might automatically come to the https://en.numista.com site. Just a thought.
I always have the EN and the FR open in different "folders", but what I really need is the toggle, when I'm on either side and I have a coin,for which I need to see what the opposite site says WITHOUT have to search it up on the other site. Pretty usefull when I'm working with documentations, which only show on the site, where it was submitted...
I'm really only interested in toggling from "COINS" in English to "PIECES" in French and I suppose you'll not set up coin data bases for many languages?
It will be possible to see the coin pages in more languages, although the exact implementation is not decided yet (only the menus and other fixed texts, or also the country names, ruler names, shape names, etc. and maybe also the descriptions and comments).