It's the giants editor available from giants software GDN. The i3d files of the carriages can be edited and the exactFillRootNode you can see with the arrow I drew on the left needs to have the rigid body collision filter group / mask changed in the menu on the right, in the new editor you can just click on the preset and find the exact fill node there and it will pre-fill the hex for you. (if image is hard to see right click and open in new tab)