Not supported — the tool is purpose-built for hot-wire cut paths, not general 3D solids. The lofted morph you see in the simulator is reconstructed from cut geometry at render time, not a real solid model.
Workaround if you really need an STL: take your two profiles, loft them in Blender / OpenSCAD / your CAD of choice. Or screenshot the 3D viewer in the tool and use that as a reference.
Workaround if you really need an STL: take your two profiles, loft them in Blender / OpenSCAD / your CAD of choice. Or screenshot the 3D viewer in the tool and use that as a reference.