Symptoms

When attempting to recreate an existing SmartObject in the SmartObject Tester Tool, the following error is seen:
SmartObjectName 'EDF.NewVendorRequest.SMO.NVR_NewVendorRequest' is Unique

However, looking at the SmartObject Browser in the Tester, an identically named SmartObject exists in the same category as the target.
 

Diagnoses

Comparing the internal name to the display name of the 2 objects revealed that the periods ('.') had been replaced with underscores ('_').
 

Resolution

Replace periods in the SmartObject Name, then use the "Get Existing Guid" feature. Afterwards, rename the Smartobject and you can successfully recreate it.