You need one field in the section access table for the reduction. That field, in the example I posted it's COUNTRY, needs to be in your regular data model too. The fields in the section access table must be in upper case.
I have no idea how to implement section access in the Qlik Sense QMC. I only know how to implement it in the script of the app. I already posted the link to the online help. I don't have 'special' knowledge that's not mentioned in the online help.