[SpineSkin("character/skin", includeNone = true)] public string skinType; 
I can make a workaround in spine create and empty skin.
If someone have a solution i would be happy, there is a big chance that im doing it wrong.
Have a nice day
IncludeNone = True doesn't return "none" in dropdown list.
@valahaha Sorry for the troubles and thanks for reporting! This was indeed a bug in the SpineSkin AttributeDrawer which existed for quite some time.
We've just pushed a bugfix to the 4.2-beta branch. The includeNone parameter is now no longer ignored and its default value has been changed from includeNone = true to false to keep the existing behavour by default. A new spine-unity 4.2-beta unitypackage is available for download here as usual:
https://esotericsoftware.com/spine-unity-download
Issue ticket URL for later reference:
EsotericSoftware/spine-runtimes2494
You're welcome, thanks for reporting!