Sidebar functionality cannot be available until Canvas opens New Quizzes for the CSS and JavaScript that gets uploaded in the Canvas Theme editor. New Quizzes can be built via the Multi Tool's Module Builder, by duplicating Assignments.
DesignPLUS Rich Content Editor tools are not available when working with New Quizzes.
New Quizzes is currently an LTI tool that is not open to the CSS/JS that gets uploaded in the Theme editor to run DesignPLUS. We are very interested in integrating with New Quizzes, so if Canvas makes this a possibility, we'll make it a priority to begin researching integration with DesignPLUS.
Since the New Quizzes LTI tool creates an assignment in Canvas, our Multi Tool's Module Builder has the ability to duplicate a New Quiz as a template just as it is able to do with other assignments but, currently, that is the extent to which we can help with New Quizzes.