This page will explain how to add another language in your Survey123 survey
Scroll over to the second Label column, or field, header
If you do not know the official language or subtag to use, please search for the language from this link: https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
The second language field header should follow this pattern
label::Description (subtag)
For example, for the Indonesian language the syntax would be
label::Indonesian (id)
Note that the description name upholds proper capitalization, or proper casing, while the subtag is completely uncapitalized
Also please note that there is only a space between the description and the open parenthesize
Here is how the final result would look like: