Quiz Scoring - Multiple Correct Answers

I am trying to create a quiz where there are multiple options and the user must select multiple CORRECT answers (eg. selecting 3 correct answers out of 6 displayed options). I'm looking for a way to score this quiz question to be worth 3 marks (1 mark for each correct answer), or to be worth 1 mark (valued at 0.33 for each correct answer). Currently, it is worth one mark which the user can only achieve if he/she selects all 3 correct answers.

I have set up the question as a graded  "Multiple Response", as "Multiple Choice" only allows the user to select one correct answer. I have found on this community discussion (https://community.articulate.com/series/4/articles/assigning-a-score-to-graded-questions-in-articulate-storyline-2) that you can score "by choice" rather than "by question", which would be ideal; however, this option is only available for some question types (Multiple Choice, Word Bank, Freeform Pick One, and Freeform Hotspot), none of which allow for selection of multiple correct answers.

Does anyone know of a way to  go around this or have any suggestions? Thank you!