Hi Pete,
in general, the dxf format has been desigend to represent geometries along with drawing styles such as colors, line thicknesses, etc. It does not directly support attribute data. While FEFLOW could export attribute data to dxf in the Classic interface, this is no longer the case in the new Standard interface. This decision has been taken as other software reading dxf, such as AutoCAD, does not support attribute data and therefore cannot read dxf files containing attributes. A long time ago, WASY distributed an AutoCAD extension with FEFLOW for enabling attribute data, but this had been developed for AutoCAD 12/13 and has not been updated later on. Thus for using attributes, I'd recommend to rather use the shape file format.
Cheers,
Peter