Since we now have a tree structure for attributes, it would be nice to group the work database identifiers into one group and the carnatic music types into another.

The most obvious way to me is to treat a non-free text work attribute type which has no options as a grouping type, since a type where you have to pick from a list of values when there are no values to choose from is otherwise pretty useless. Right now though, if we add a non-free text work attribute type but don't add any options for it, it will just show an empty select.