How can I increase the limit of UV's channels for skeletal mesh?

Good evening. Is there any way to increase the limit of UV’s channels for skeletal mesh from 4 to 6? Maybe, I should change something in project settings? Sorry, I don’t know right category for this question.

It’s very strange, but I’m not sure about the limit now, because I can add uv channels using unreal’s editor. But still can’t export it from blender.