Maybe this will help, maybe not. We use two very different list of categories. The first set of categories is for the incident creation that categorizes what the type of problem is. IE Network and then Wireless or Network and Ethernet. The resolution uses a different set of categories that categorizes what the analyst did to fix the problem. IE Training, account issue, password reset, configured windows etc.
Our thinking was that in the incident we wanted to know what types of problems are users having. The resolution tells us what our analysts are doing to fix the issues. It's two very different questions and answers. Using the same category for the resolution seems like a waste of time and effort. I think you will find the resolution categories fascinating.