Context menu item to bulk extract model file materials to a folder.

ExtractModelMaterials.cs

#if UNITY_EDITOR
using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEngine;

static class ExtractModelMaterials {
    static readonly string[] ModelExtensions = {
        ".fbx",
        ".obj",
        ".blend"
    };
    
    [MenuItem("Assets/Extract Materials")]
    static void Extract() {
        var outputPath = EditorUtility.OpenFolderPanel("Select Materials Folder", Application.dataPath, string.Empty);
        if (string.IsNullOrEmpty(outputPath)) return;
        if (!outputPath.StartsWith(Application.dataPath)) {
            return;
        }
        
        outputPath = "Assets/" + outputPath[Application.dataPath.Length..];
        
        AssetDatabase.StartAssetEditing();
        foreach (var guid in Selection.assetGUIDs) {
            var assetPath = AssetDatabase.GUIDToAssetPath(guid);
            if (string.IsNullOrEmpty(assetPath)) continue;
            
            ExtractMaterials(assetPath, outputPath);
        }
        AssetDatabase.StopAssetEditing();
    }
    
    [MenuItem("Assets/Extract Materials", validate = true)]
    static bool ValidateExtract() {
        if (Selection.count == 0) return false;
        return Selection.assetGUIDs.All(IsModel);
    }
    
    static bool IsModel(string guid) {
        var path = AssetDatabase.GUIDToAssetPath(guid);
        if (string.IsNullOrEmpty(path)) return false;
        
        var extension = Path.GetExtension(path);
        if (ModelExtensions.Contains(extension)) {
            return true;
        }
        
        return false;
    }
    
    public static void ExtractMaterials(string assetPath, string destinationPath) {
        var hashSet    = new HashSet<string>(64);
        var enumerable = AssetDatabase
            .LoadAllAssetsAtPath(assetPath)
            .Where(x => x is Material);

        foreach (var item in enumerable) {
            var path = System.IO.Path.Combine(destinationPath, item.name) + ".mat";
            path     = AssetDatabase.GenerateUniqueAssetPath(path);
            
            var value = AssetDatabase.ExtractAsset(item, path);
            if (string.IsNullOrEmpty(value)) {
                hashSet.Add(assetPath);
            }
        }

        foreach (string item2 in hashSet) {
            AssetDatabase.WriteImportSettingsIfDirty(item2);
            AssetDatabase.ImportAsset(item2, ImportAssetOptions.ForceUpdate);
        }
    }
}

#endif