How can i create two buttons in the inspector in editor with space between the buttons without overriding existing other controls ?

By the default this is the script attached to a empty gameobject in the hierarchy:

 namespace CBX.TileMapping.Unity
 {
     using UnityEngine;
  
     public class TileMap : MonoBehaviour
     {
         public GameObject Prefab;
         public bool randomScale = false;
  
         public int Rows;
         public int Columns;
         public float TileWidth = 1;
         public float TileHeight = 1;
  
         [HideInInspector]
         public Vector3 MarkerPosition;
  
         public TileMap()
         {
             this.Columns = 20;
             this.Rows = 10;
         }
  
         private void OnDrawGizmosSelected()
         {
             var mapWidth = this.Columns * this.TileWidth;
             var mapHeight = this.Rows * this.TileHeight;
             var position = this.transform.position;
  
             Gizmos.color = Color.white;
             Gizmos.DrawLine(position, position + new Vector3(mapWidth, 0, 0));
             Gizmos.DrawLine(position, position + new Vector3(0, mapHeight, 0));
             Gizmos.DrawLine(position + new Vector3(mapWidth, 0, 0), position + new Vector3(mapWidth, mapHeight, 0));
             Gizmos.DrawLine(position + new Vector3(0, mapHeight, 0), position + new Vector3(mapWidth, mapHeight, 0));
          
             Gizmos.color = Color.grey;
             for (float i = 1; i < this.Columns; i++)
             {
                 Gizmos.DrawLine(position + new Vector3(i * this.TileWidth, 0, 0), position + new Vector3(i * this.TileWidth, mapHeight, 0));
             }
          
             for (float i = 1; i < this.Rows; i++)
             {
                 Gizmos.DrawLine(position + new Vector3(0, i * this.TileHeight, 0), position + new Vector3(mapWidth, i * this.TileHeight, 0));
             }
  
             Gizmos.color = Color.red;  
             Gizmos.DrawWireCube(this.MarkerPosition, new Vector3(this.TileWidth, this.TileHeight, 1) * 1.1f);
         }
  
         public void GenerateNew()
         {
  
         }
  
         public void DestroyBlocks()
         {
  
         }
     }
 }
 

And this is how it looks like in the editor in the inspector:

Now i created another script:

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 using CBX.TileMapping.Unity;
 
 [CustomEditor(typeof(TileMap))]
 public class CustomButton : Editor
 {
     public override void OnInspectorGUI()
     {
         TileMap Generate = (TileMap)target;
         if (GUILayout.Button("Generate Map"))
         {
             Generate.GenerateNew();
         }
 
         if (GUILayout.Button("Destroy Blocks"))
         {
             Generate.DestroyBlocks();
         }
     }
 }
 
 And now the editor in the inspector it looks like this:

All the properties variable checkboxes now gone or hided by the two buttons.

How can i add the two buttons and also show the checkboxes and all other controls/properties ? And how can i add some space between the two buttons so i don't click the wrong one by accident ?