Follow the instructions here to add an .XML file:
https://docs.vmware.com/en/VMware-Workspace-ONE-UEM/2102/ProdProv_All/GUID-0D7CA897-16EE-4720-B377-46DA916DCEBC.html

Add ALL of the values you want populated to the same .XML file
No real reason to push additional custom XML profiles
Then publish here:https://docs.vmware.com/en/VMware-Workspace-ONE-UEM/2102/ProdProv_All/GUID-5A5C7558-08D9-4BC1-BFF7-69A7C84C489A.html

And enable as Custom Attribute