When creating an actor blueprint the default scene root's category setting provides the option to change its category and provides multiple options. However, if a new component it added, the drop down will be grayed out. The only way to use the drop down is to select the component in the variables list. Even then the only option available is default.
Result: While the scene component in selected in the component hierarchy the category cannot be changed
Expected: The category drop down would working in the same way as it does for the default scene root that is generated when the actor is created (The drop down is available and provides multiple options)
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-75285 in the post.