Actions - Attribute Mapping

Summary:

Trying to map an attribute of 'Activity' to a User-defined value of 'Task' on an action that will be used in an action template for Case Management. Not a default attribute, where is the location to add custom attributes to the attribute mapping drop down-list?

Content (required):

See attached screenshot from demo.oracle - it appears it is possible to add custom attributes to the drop down-list though I am not able to find documentation on where this would be configured. Hoping someone in the Community might be aware of where you a required to perform this configuration.

Version (include the version you are using, if applicable)