why you want to go back to S-Edit? you just need to add simulation parameters to the spice file and simulate it! ledit used to obtain the GDS2 file that you are going to send for fabrication. but before you send, you need to simulate it to make sure that the circuit is working fine (in tspice). I cannot see any s-edit here! ledit is stand alone simulation software. so you can simply merge them as you said