Thanks for the suggestion, this will be improved in the upcoming 3.2 release and included in the next beta release. We've increased the field to 3 lines and it now accepts the enter key.
How would you like to use the variable? E.g., would you like to use it in an email alert such as a subject?
The $GROUP variable already exists (http://www.eventsentry.com/documentation/help/html/configvariablesdetails.htm), but it may not exist in the context you need. Please let us know.