I will try to example our situation.
We use what we named "template courses". These are courses that are the original and them we create the real courses students use with Moodle procedures to do so. Namely the "upload courses" feature.
So something to bear in mind, in Moodle you have categories for organizing your courses, and you have categories for your question bank. They are totally apart from each other BUT, as I will try to show you further in the explanation of our case, they are somewhat "connected".
We have a course category "Course Template", inside we have all our courses, some in sub categories. Assuming "Course Templates" has our main category, then we have courses in these main category, these are the courses where we don't need to share question, and as such, the questions for these courses are at the course level. But them we have some courses that need to share questions, so we made another category, for example, "Template DMIF". Inside "Template DMIF", we have a number of different courses that share the questions inside DMIF and because there are some that share part of these questions and have some that are specific we create another category, "Template MBCP". These are all course categories.