Basically making a command like :
curl -sk -X GET 'https://URL/api/mdm/devices/customattribute/search?deviceid=12345' -H 'Authorization: Basic ABC' -H 'aw-tenant-code: DEF' -H 'accept: application/json;version=1'
If the device is no more enrolled, the answer is :
Once the device is re-enrolled, the answer is the custom attributes for the device.
Can someone forward that to the engineering ?