Is it possible with the group function to group a treetable by more then one data item. Mybe something like mytable.group(‘city’, ‘name’).
You can apply .group few times
http://webix.com/snippet/94fad414
The key point here, use some.data.group instead of some.group ( when the method is called against a component, it removes the previous grouping, when the method is called against datastore it allows to add an extra grouping on top of the previous one )