In some cases, duplicate custom attributes may have been created by accident. For example, two operators creating custom attributes that cause attributes with the same Reference Name that is created at the same time through separate browser sessions.
This causes an issue as you cannot change attribute name to anything else as both attributes having the same Reference Name which cannot be changed in the UIand you will get an error as shown below. You will also not able to add new attributes in this scenario.
Once the attribute is created, that could not be deleted, however, we can rename the attribute. Please contact RSA Customer Support and reference this article for a solution.