I attempted the following language codes in the same localized field of a .tab:

• sr-Cyrl (Serbian language in cyrillic letters)
• sr-Latn (Serbian language in latin letters)
• zh-Hans (simplified Chinese)
• zh-Hant (traditional Chinese)

I have been bounced back by

Error: Parameter "data[*][*]" must be an object that maps valid language codes to single line strings without tabs or trailing spaces, e.g. { "en":"String in English", ... }

Downcasing of the scripting codes did not help.

I was to reduce the offered selection to:

• sr
• zh

Note that the codes meet RFC 5646 (2009, #2.2.3. Script Subtag) and ISO 15924, therefore also BCP 47. Consider ISO 3166 variants as well, e.g. en-US.