Want replace a current object with one inside array the object being replaced with is prefab

I haven't tested the script but give it a try

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine.UI;
 using UnityEngine;
 
 public class SpawnSetting1 : MonoBehaviour
 {
     public bool opt;
     
     private GameObject current;
     
     [SerializeField]
     private GameObject[] prefabs;
     
     private GameObject[] instances;
 
     private void Awake()
     {
         instances = new GameObject[prefabs.Length] ;
         SwapWith(0);
     }
     
     void OnGUI()
     {
         if(opt)
         {
             if(GUI.Button(new Rect(Screen.width - 160,0, 160, 30), "make sphere"))
             {
                 SwapWith(1) ;
             }
         }
     }
 
     public void Options()
     {
         opt = !opt;
     }
     
     public void SwapWith( int prefabIndex )
     {
         if( instances[prefabIndex] == null )
         {
             instances[prefabIndex] = Instantiate( prefabs[prefabIndex] ) ;
         }
         
         if( current != null )
         {
             instances[prefabIndex].transform.position = current.transform.position ;
             instances[prefabIndex].transform.rotation = current.transform.rotation ;
             current.SetActive(false);
         }
         
         current = instances[prefabIndex];
         current.SetActive(true);
     }
 }

INITIAL ANSWER

Supposing you want to hide the current one and show a new one :

  if(GUI.Button(new Rect(Screen.width - 160,0, 160, 30), "make sphere"))
  {
      current.SetActive(false);
      current = test[1];
      current.SetActive(true);
  }

test must contain objects currently in the scene. If you have prefabs, the code won't be the same.