This idea has been developed and deployed to Canvas

Currently in quizzes the "Show Question Details" is limit to only display when there are 25 questions or less. Anything above 25 prevents this checkbox from being clicked. 

We have had numerous instructors ask about this feature and for the possibility of it to be increased. Based on a previous feature request, I believe question banks will display up to 50 questions. https://community.canvaslms.com/ideas/1196-raise-the-50-question-question-editpreview-cap-for-questi... 

Comments from Instructure

This idea was completed with general availability of Quizzes.Next.  You can find more information about the overall project in the Quizzes.Next User Group.‌

• Quizzes.Next is now available for all paid accounts.
• Quizzes.Next documentation will live in the Quizzes.Next User Group until July 14, 2018. On July 14, 2018, all of the documentation will be moved to the Canvas Guides in the Canvas Instructor Guide or Canvas Student Guide. 
• Quizzes.Next updates will be included in the Canvas Release Notes. This includes new features, updated features, and relevant fixed bugs. New and updated features will be deployed to Quizzes.Next near the same time as the Canvas release. Fixed bugs may be deployed at any time.