Copy clip assets from selected multiple model assets. Select assets and right click and find menu Model/Duplicate animation assets. Hotkey is Alt+D.

AnimAssetDuplicator.cs

using System.IO;
using UnityEditor;
using UnityEngine;

namespace Assets.Editor
{
    public class AnimAssetDuplicator
    {
        [MenuItem("Assets/Model/Duplicate Animation Assets &d")]
        public static void DuplicateAnimationAssetsInThisFolder()
        {
            foreach (var gameObject in Selection.gameObjects)
            {
                string path = AssetDatabase.GetAssetPath(gameObject);
                Object[] objects = AssetDatabase.LoadAllAssetsAtPath(path);
                foreach (Object obj in objects)
                {
                    DuplicateAnimationClip(obj as AnimationClip);
                }
            }
        }

        private static void DuplicateAnimationClip(AnimationClip sourceClip)
        {
            if (sourceClip != null && !sourceClip.empty && !sourceClip.name.Contains("preview"))
            {
                string path = AssetDatabase.GetAssetPath(sourceClip);
                path = Path.Combine(Path.GetDirectoryName(path), sourceClip.name) + ".anim";
                string newPath = AssetDatabase.GenerateUniqueAssetPath(path);
                AnimationClip newClip = new AnimationClip();
                EditorUtility.CopySerialized(sourceClip, newClip);
                AssetDatabase.CreateAsset(newClip, newPath);
            }
        }
    }
}