Just checked in this piece to the master branch of the Go-OO repository, to support sorting of DataPilot’s field members using custom sort lists. I’ve extended the popup window I wrote for the hide field members functionality to provide this additional sorting functionality. The result is the following popup window:
In the upper half of the window I’ve added a menu-like control, with the custom sort lists being provided in the submenu. The UI is fully functional, but still a bit rough around the edges. The custom sort list submenu, in particular, may need some additional work to handle a large set of custom sort lists, a sort list that is very long, or stuff like that. But as long as your sort list is in modest size, it should work just fine.
This feature didn’t make it in to 3.1 since we are in a stabilization phase for 3.1. But as soon as we branch master for the stable 3.1 branch, I will enable this feature in the default build in the master branch.