I already found out how to hide closed question from "Unanswered", "No selected Answer" and "No upvoted answer" question list.
However, I still need to hide them from "Questions", i.e. from:
Do I need to change the function qa_db_qs_selectspec for that or another one? In which query should I insert AND closedbyid IS NULL ?
You can add it inside function qa_db_qs_selectspec(...) in the $selectspec['source'] part.
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