If the data is nested (two levels), it seems to work for the first column
(the one with the folders) but not the other columns (http://webix.com/snippet/9555d0b1).
I am a first-time Webix user (as you may have guessed and am very impressed with this excellent support (despite the fact that, technically, there is no support for the free version :-).
All my problems are solved, and I’ve learned some extra stuff.
By the way, what is it that will be fixed in 3.0? The need to copy the columns? That might save some new users problems like I had, but once you know the answer, it’s really no big deal.