Things like weapons, armor, hats in particular. Used to be able to Transmute them, make this look like that, doesn't seem possible anymore now that this new appearance system is out. Am I missing something or has this ability been removed ?
Right click the item you want to use as a transmute. Add to the Appearance Library. Open the Appearance tab. Left click the item which appearance you want to change. Select the new skin you added earlier. Click 'Save'.