Thanks for the question. Before answering, I have a few questions back to you.
1. what do you mean by input tensors? Do you mean tensors you plan to input into another code? Or is it a tensor with a special property?
2. we do offer the ability to save ITensors to the HDF5 file format using the Julia version of ITensor (ITensors.jl). We are working on that same capability for the C++ version of ITensor and it is almost done. Would that suit your purposes?