When creating an enumeration constraint on a Data Type the following happens:-

• Click "Add" blue icon and a new row is created
• Enter a value
• Before clicking the check/tick click the "Add" blue icon again
• Another new row is created.
• Enter a value.
• Click the blue check/tick icon on the row.
• Both rows are committed.

You'd think the blue check/tick icon would only affect a single row as it is shown individually for each row. It would also be consistent with the behaviour on the main Data Type editor list.