From the VkSamplerCreateInfo javadoc:
SAMPLER_ADDRESS_MODE_MIRROR_CLAMP_TO_EDGE indicates that the mirror clamp to edge wrap mode will be used. This is only valid if the VK_KHR_mirror_clamp_to_edge extension is enabled.
You will find VK_SAMPLER_ADDRESS_MODE_MIRROR_CLAMP_TO_EDGE in KHRSamplerMirrorClampToEdge. You must explicitly enable the VK_KHR_sampler_mirror_clamp_to_edge extension to use it.