With SD 1.2.5 we removed all ServiceDesk projects. The field configurations that were created for SD were still present. This is expected though annoying, consistent with the rest of removing SD.
The field configurations were not listed in any active or inactive Field Configuration Schemes

However in this case the Delete link was not present for the SD field configuration so it could not be deleted. This is not what I expected and leads to unused field configuration schemes cluttering up JIRA.