From experience the mixed cabin option is *usually* available for simple round trip ticket, maybe open jaws but definitely not for multi-city.
I want to book, e.g. MAD-DOH-SGN, with first (daytime) seg in Y and second (overnight) one in J. Is this possible? Not on QR web site, not direct with QR or any OTA I've tried so far... Just to make a rather expensive ticket a bit cheaper. Thanks.