Adding an element to List a .asset file of ScriptableObject

I created and asset file of this ScriptableObject:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 namespace BuildingPrefabs
 {
     [SerializeField]
     public class BuildingBlocksManager : ScriptableObject
     {
         [SerializeField]
         public List<BuildingBlock> prefabsList = new List<BuildingBlock>();
     }
 
     public class BuildingBlock
     {
         [SerializeField]
         public GameObject block;
         [SerializeField]
         public bool isActiveBlock;
 
         public BuildingBlock() {
             block = null;
             isActiveBlock = false;
         }
         public BuildingBlock (GameObject block_, bool active = false)
         {
             block = block_;
             isActiveBlock = active;
         }
     }
 }

How do I add and element to the list in .asset file of this ScriptableObject?