Appearance of Lesser Cheetah cloak of Amedio can't be changed while cloak is equiped.
Steps to reproduce:
1) Take on cloak
2) Press R and choose "Craft" then "Modify item appearance.
3) Make sure that option "Modify cloak appearance" doesn't appear in crafting menu.
P.S.
Maybe it's is designed to be that way, in that case line "This item can't be modified" should be added into description of an item.
