One thing that's not clear from your question is whether a given question can appear on more than one exam - if so, that would mean the association between Exam and Question entities would need to many to many.
If that's your domain model, you can do this with a standard Mendix page without the need for a microflow. Create a Master Detail page using the new page wizard. The Master would be a list of Exams, the detail would contain a Reference Set Selector of the questions for the selected Exam. Just be sure to commit changes when the question list is changed for an Exam.
Hope that helps,
Thanks for your answer. I have it so a question can only appear in one exam, with the domain model a one-to-many, so I would use the pool to disassociate from an existing exam and then associate unassociated questions to a new exam. As someone would only be given a second exam if they fail the first so I don't want to allow the same questions in multiple exams.
I was trying things in the meantime since and found a way which works. Having a datagrid of exams from database, then below it a dataview listening to the exam datagrid. Then within that dataview a datagrid of questions from database.
So I can select an exam then multi-select questions and press a button in the question datagrid which calls my microflows and passes both the exam and question list as paramaters.