There is no such thing. Any question prefaced with those words is not quick; an important question that cannot wait. Anyone saying this wants to shoehorn a question into what you are doing.
A quick question can be answered by yes or no. Rarely, does some preface an easy question with a qualifier. They just ask the question.
I’m sensitized to the term because so many people use it. Why? Is it necessary to draw attention to the question or the attempt to disarm me to something that is bigger than it is presented? Apparently.
If you have a question, ask it. If it will take time to discuss an answer or is sensitive, pick a good time to discuss it properly. I will comply.
When I hear “quick question”, my defenses go up and I’m suspicious. It feels almost like I’m being maneuvered. In some cares, the person asking may not even be aware of the cliche they are promoting. Quick question denotes an equally quick answer. That’s not usually the case. Any question I’m asked gets my full attention and my best advice. I would rather being told this is important and they appreciate my opinion. That’s more honest.
I do not charge by the answer or the time needed. You get my best effort regardless of quick or long.