Enable but hide a language

I wonder if I’m missing something obvious because I can’t find anyone else asking about this!

I have a client site. They want to be able to add different languages themselves at their leisure. And of course with q-translate-x, they can! However, as soon as the language is activated, it shows up on the public facing site via the language switcher.

Is there a way for a language to be active (so that you can enter text for it in the admin area), yet hidden (so it isn’t yet served on the live site) ?

Many thanks in advance.