My survey has 20 questions (scored from 1 to 5)
What type of question? List(radio)?
But there are three subquestions in item 15
And what is this? An array - because of the subquestions?
As example:
If you have your answer options coded "1", "2",... and not "A1", "A2",...
and the answer options of the array as well,
you can use Expression Manager to calculate your score:
{sum(Q1.NAOK,Q2.NAOK,Q3.NAOK,...Q20.NAOK,max(Q21_SQ001.NAOK,Q21_SQ002.NAOK,Q21_SQ003.NAOK))}
Here I named your "item 15" with the subquestions "Q21".
But without knowing your exact structure ...
Best - as usual - is to send a small example of your survey as *.lss export.
Joffm