I use a rather big question bank for a yearly course. There usually are various variations of a question and they are all ordered in a category tree. For the training phase I want to use some of the questions while reserving the remainder for the final exam. The exam questions usually are drawn at random from specified categories. It would be nice if I could mark some questions as "used for training" in a specific course so as to *exclude* them from the random selection for the exam.
Currently it seems only possible to *include* certain tags but not the opposite. As a work-around I create temporary categories into which I export the training questions. However, this approach reaches its limits when teaching one and the same course in parallel. I have tried to mark all questions with an "exam" tag but that quickly becomes quite over-whelming.
I propose to select quiz questions by excluding certain tags. From a technical perspective this is rather simple. Though, the UI is not quite ready for this. So I do see some difficulties and, alas, have nothing else to offer then this idea as I do not have any developer skills.
Thanks for your consideration. Please comment!
Sincerely,
St. Mueller
What version of Moodle are you using?
Version is 4.1. Forgot to mention, sorry! The behavior was the same on versions 3.x.
I have just had a look with Moodle 4.3 and there are some additional filtering options, but not a NOT from what I can see.
In my opinion adding a condition in the question bank filters like so:

Should do what you like, Match Questions that have none of the tags you are looking to exclude. In my case somehow this does not work as I would expect it to.
As I see it, excluding a tag this way only works if that specific tag is the only tag on that question. I don't know if this is a bug I should report to the tracker or if it is a wanted feature.
That looks exactly like what I was looking for. Where did you find this and and what version of Moodle?
I am on Moodle 4.5.3 in the course question bank

Awesome! Good to know that this feature got implemented. My Moodle- and all other servers are currently unavailable due to a bad flash flood drowning it all. As soon as I get it up and running again, I shall try it out.