The problem is that a multiple choice question consists of several sub-questions (each answer option is a yes/no=checked/not checked answer) while for a single choice question you only have to store one answer for the whole question.
Because of this technical difference, there is (to my knowledge) no easy way to switch between these question types.
Best regards/Beste Grüße,
Dr. Marcel Minke
(Limesurvey Head of Support) Need Help? We offer
professional Limesurvey support Contact: marcel.minke(at)survey-consulting.com'"