Add "severity" as a "group by" option in Defects

@krmorse We really like this app and are using it for defect tracking by state. But it doesn't allow for tracking by "severity".
I saw that the "group by" option has some standard fields and a couple custom fields but not all the fields.

Is it possible to add all the fields in the defects here? It will help us a lot and this would remain a one stop shop for all kinds of tracking! 
