Thanks Anthony,
I can see the underlying thinking of this mass import.
But this is what I experience:
I import one quiz from course A to course B and then one quiz from course B to course C.
Then course C contains all questions, categories and resource files from course A and B. Most of them are not wanted and we are talking 800 not wanted questions in 40 categories and a lot of files and folders.
I end of having every course containing every other course.
On top of that I'm not able to delete the unwanted categories using the 'Edit categories' interface (after deleting the questions). I get a warning message saying the categori has questions in it (telling me to move the questions first). That is why I have to manually delete these empty categories directly from the database's mdl_question_categories.
Besides my fellow teachers complain that they cannot edit some of the imported questions as they belong to the originator.
So something unhealthy happened to my database during these backup's and restore's during the last month.
The safe way seems to be:
1. Export the wanted questions to the desktop as MoodleXML including the categories (tick the 'to file').
2. Open just that one file in a text editor, and do a FindAndReplace to replace all occurrences of course related resource links like "http://mydomain.com/file.php/32/". Substitute '32' with the course number for the destination course.
3. Make a zip file of the wanted resourse files. Download this to the desktop.
4. Upload and unpack the zip file to the file system of the destination course.
5. Import the questions including the categories (tick the 'to file') into the destination course.
6. Author new quizzes using the imported questions.
Best regards
Morten