Hello everyone! I'm new to this community so I'm still a bit lost here. This does sound like an interesting and a fun project though so I'd be happy to contribute!
I'm from Finland so Finnish is my native language. I also speak (pretty much) fluent English and Swedish. Also I'm currently studying French. Gosh, I hope that I'm writing this to the right place.
Actually, there already is a script ("Tatoeba default languages") by FlamingTofu (that lets you move the languages you use most to the top of the drop-down list and call them whatever you like (including their native names). The script can be installed from here:
Ich habe in den letzten Tagen keine E-Mail-Benachrichtigungen von Komentaren zu meinen Sätzen bekommen, obwohl die automatische Benachrichtigung aktiviert war. Kann es mit der zurückliegenden Störung zusammenhängen?
has a bullet item at the top entitled "How to change the language of a sentence". However, it refers to a nonexistent anchor, so clicking on the item does nothing. It would be nice to fix this before the content is used as the basis for a wiki page.