Indeed it is tricky to access the elements/nodes when you use points to constrain the meshing process. There are basically two options: Either you create many points in 3D within you zone of interest and use the point map to select the elements, or you use surfaces rather than points for the mesh generation, so that FEFLOW can set up groups of elements etc. However, for the second option you'd have to have CLEAN surfaces for the tunnels, without any intersections or self-intersections, which is sometimes hard to achieve, even with 3D design software.
