To update custom property issue a PUT request to the /ccadmin/v1/itemTypes/promotion/{id}
endpoint on the administration server with the ID of the existing custom property. The following example changes the label displayed for the campaign
property:
{ "id": "promotion", //this is the ID of the item-type item "specifications": [ { "id": "campaign", //this is the ID of the property "label": "Discount Source" } ] }