Hi Georg, great that you found this problem, If you like you can change yourself and apply the code change to this discussion after it will be validated and the framework updated. Else I can do the change but that will take some time as I'm at Qlik user conference Qonnections in Orlando the week to come.
I rewrote the code and it works just fine for me. Please see the attached picture:
LET vL.Store_Select_tmp_new='['&'$(vL.TempField)'&'], '&'$(vL.Store_Select_tmp_new)'; // Concatenated statement
LET vL.Store_Select_tmp_new= '$(vL.Store_Select_tmp_new)' & '[' & '$(vL.TempField)' & ']' & ',';
Notice that I only modified the code for CASE DEFAULT in the control structure because at the moment I do not need the others. It would be great if you could apply this quick fix to the others and in future releases of QDF as well
All the best