Thank you very much for your response.
I have reviewed this answer as well as similar discussions previously, but I still find myself unclear about certain implementation details in Is it possible to program (from scratch) a 2nd-order tetrahedron in FeniCs Legacy?. Specifically, I am unsure how to implement the I/O interface following the lines of dolfinx.io.gmshio and dolfinx.plot.vtk_mesh to read higher-order meshes in legacy FEniCS. Additionally, I am having some difficulty understanding the statement “ordered in the UFC fashion, not VTK or Gmsh node ordering”. Could you please provide further clarification on this matter?
I would also like to inquire if it is possible to accomplish this with concise Python code instead of C++ code, and if there are more applications of higher-order meshes in legacy FEniCS that might be relevant to my inquiry, such as Support for curved edges.
I would greatly appreciate any further guidance or insights you might be able to provide. 