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Your LimeSurvey version: [5.4.15]
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I am querying the JSON RPC API for responses and questions.
The  list_questions  endpoint does not show Sub Question Texts if Question type is "multipleshorttext".
The only way to get those Texts was via  export_responses  if the "$sHeadingType" is set to "full". The response to this is unfortunately really hard to parse, since the "keys" in the json can be "anything" depending on the question text.

Is there an easier way?

Alternatively, is there a complete list of keys the response can include for all the HeadingTypes (full, abbrv code)?

I just found that "get_question_properties" gives me these.

I still have a hard time, finding out what the excact answer keys for these requests are. It references: api.limesurvey.org/classes/Question.html but the properties listed there do not match at all.