Hi,
it works too, name your GameObject "Category A / Ennemy 3" and it will be categories based on the / character.
But I don't really recommand this, prefer using hierarchy:
Category A
Ennemy 3
Where Category A is an empty GameObject. I always do that, I even sometimes create an empty object with a an empty name, then it doesn't appear in the hierarchy, and I put all the unnecessary stuff for daily work on projects, very effective and clean.
Bye,
Jean