You can adapt the solution with copying to the large tensor from above, (I must admit I still don’t fully understand whether you want one or two tensors as a result): I think you can do
out_tensor[i, :length, ...] = single_embedding_per_point[i, None]

and similar to use broadcasting (with the new singleton dimension generated by the None index for the :length index on the left hand side). Use single_embedding_per_point[i][None] if it’s a list of tensors rather than one large tensor.
Best regards
Thomas