What exactly do you mean here?
You can update stopwords in as many languages as you want (I'd recommend keeping a test list for each language in a multilingual project saved in a separate folder in the project). The catch is that you can only have the project set to one language at a time (and thus only be able to use one stopwords list).
I haven't had a chance to try yet, but I suspect you could also manually make a multilingual stopwords list for word frequency queries by combining two or more lists, as long as no more than one of the languages has no spaces between words (like Chinese or Japanese). When I use Japanese, it still can detect word boundaries for English words in the project because of spaces, but if I had Chinese as well, it wouldn't have both dictionaries simultaneously. This wouldn't work for autocoding themes because it wouldn't be able to parse noun phrases in multiple languages.
So if you mean being able to query multiple languages in a single project, there is definitely the alternating by changing the project language option. And there is likely a manually combined stopwords list option as well that would work at least for word frequency queries.