There were acutally two issues

• The original issue reported here, which was mostly already fixed elsewere, as verified by mod/quiz/tests/behat/editing_switch_bank.feature tests.
• The real issue is: to use questions from from another question bank, the capability you actually need is moodle/question:useall or usemine. So, the code should not have been checking moodle/question:managecategory here. That is what I have now fixed using this issue.

Original report:

To reproduce:

1. Create a role "questionbankmanager":
   • no basis role
   • context type "category"
   • "moodle/question:managecategory" -> Allow
2. Create a course category "testcategory"
3. Create a course "course1" in "testcategory" and a course "course2" in "testcategory"
4. Create a user "user1" and "user2"
5. Enrol "user1" to "course1" with role "editingteacher"
6. Enrol "user2" to "course2" with role "editingteacher"
7. As "user1" create default question bank in "course1"
8. As "user2" create default question bank in "course2"
9. As "admin" assign role "questionbankmanager" to "user1" on "testcategory" context
10. As "user1" create a test activity, open the test activity, go to "questions", add a question from question bank.
11. Click "Switch question bank"
12. In the autocomplete field "Other question banks" you will see the default question bank from "course2" which you are not supposed to see -> Bug