This is about AllowedValues for ItemDefinition.
Currently a general Expression text area is available, and user can place some Comma-separated-values in it, which the editor can handle and transform into Enumeration.
This feature request is pitching for something different.
In the Enumeration view, have a text area input modal dialog which would accept one value per line. This way the modeler can copy-paste from Excel (column) in the editor to facilitate the load of the business data dictionary