Hello there, @katrien_delangh ...
I believe the reason why you cannot currently select Canvas Studio videos inside of New Quizzes is because both Studio and New Quizzes are built as LTI external tools. So, as of right now, both of those tools don't really "talk" to each other, and I'm not sure if Instructure has any plans to be able to embed Studio videos into New Quizzes.
However, I was still able to embed a Studio video in a New Quiz multiple choice question.
What I did was harvest the embed code from a Studio video. How do I get a public link or embed code for media... - Canvas Community Then, I went into my New Quizzes quiz and created a new multiple choice question. I was able to use the Rich Content Editor tools to add the embed code to the question stem. As you can see from the above image, the Studio video is displayed above the answer choices.
Do you think that this would be a workable solution for you? Looking forward to hearing back from you soon. Take care...be well.
Thanks for sharing your workaround. I work in a K-12 district and have teachers who are looking to make use of Studio content with New Quizzes. Studio is new to use and has some nice features, but not being able to use them with New Quizzes is a barrier for use for some teachers. Having your workaround will help, but hopefully, the integration of the two tools is on the priority list for Instructure.