How to create a complex material in an Editor-Script? C#

Hi, I created an Editor-Script which takes the materials of an GameObject and replaces them by existing materials from the Resources-Folder. Now I want my script to replace the old materials by new materials which I create in the script! I got this fare:

 GameObject SelectedObject = Selection.activeGameObject;    
 Material[] materials = SelectedObject.GetComponent<Renderer> ().sharedMaterials;
 int Arraylength = materials.Length;
 
 for (int i = 0; i < Arraylength; i++) {
     string matName = materials [i].name;
     
     if (matName == "Test_Material_01") { 
         int var = i;
 
         Material mat  = new Material (Shader.Find("Standard"));
         AssetDatabase.CreateAsset(mat, "Assets/Imports/Object/Materials/NewMat_" + var + ".mat");
     
         materials [var] = mat; 
         SelectedObject.GetComponent<Renderer> ().sharedMaterials = materials;
         
         ...

This code creates a new white Standard-Shader and saves it!

The Problem: I don´t know how to build more complex Standard-Shaders in this script. With textures, colors, smoothness, metallic look and so on...

Can anybody help? Thank you!!