DummyComponent.cs

/*
 this is an example
*/

using System.Collections;
using System.Collections.Generic;
using UnityEngine;


[System.Serializable]
public struct SomeTestStruct{
	public int field1;
	public int field2;
	public int field3;
	public int field4;
}



public class DummyComponent : MonoBehaviour {

	[StructCopy] public SomeTestStruct structA;
	[StructCopy] public SomeTestStruct structB;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
		
	}
}

StructCopy.cs

using UnityEngine;

public class StructCopy : PropertyAttribute {
}

StructCopyDrawer.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

[CustomPropertyDrawer(typeof(StructCopy))]
public class StructCopyDrawer : PropertyDrawer{

	private static Dictionary<string, object> Clipboard = new Dictionary<string, object>();


	public override float GetPropertyHeight (SerializedProperty property, GUIContent label)
	{
		var additional_height = 0f;
		if (property.isExpanded) {
			additional_height = property.CountInProperty () * EditorGUIUtility.singleLineHeight;
		}

		return 2 * EditorGUIUtility.singleLineHeight + additional_height + 5;
	}

	public override void OnGUI (Rect position, SerializedProperty property, GUIContent label){

		var left = new Rect (position.position, new Vector2 (position.width / 2, EditorGUIUtility.singleLineHeight));
		var right = new Rect (new Vector2(left.position.x + left.width, left.position.y), new Vector2 (position.width / 2, EditorGUIUtility.singleLineHeight));

		if (GUI.Button (left, "copy this")) {
			var obj = property.serializedObject.targetObject;
			var type = property.serializedObject.targetObject.GetType();
			var field = type.GetField (property.name);
			var val = field.GetValue (obj);

			if (Clipboard.ContainsKey (property.type)) {
				Clipboard [property.type] = val;
			} else {
				Clipboard.Add (property.type, val);
			}

		}

		GUI.enabled = Clipboard.ContainsKey (property.type);
		if (GUI.Button (right, "paste into this")) {
			var val = Clipboard [property.type];

			var obj = property.serializedObject.targetObject;
			var type = property.serializedObject.targetObject.GetType();
			var field = type.GetField (property.name);
			field.SetValue (obj, val);
			property.serializedObject.ApplyModifiedProperties ();
		}
		GUI.enabled = true;

		position.y += EditorGUIUtility.singleLineHeight + 5;

		EditorGUI.PropertyField (position, property, true);



	}

}