I don’t think there would be that many of them where using a comma separated list would be that much trouble.
But a “global” class would be easier.
If it’s going to be done I guess now while that area of code is being worked on would be the opportune time to do it.
Think as I might, ATM the best I can come up with as a descriptive value is “non-category”. It just feels to me that there should be something, anything better than that, but I got nothing.