Having a hard time getting custom editor script changes to save

Hello, I have been trying to get a custom editor script to persist changes that I make in the editor but nothing that I have tried has worked so far. I have the following list in a monobehaviour:

     public class SnapPoint : MonoBehaviour
     {
         public List<SnapPointWhiteList> SnapPointWhiteList = new List<SnapPointWhiteList>();
     }

The snappoint class is defined as:

     [Serializable]
     public class SnapPointWhiteList
     {
         public BuildingPieceBehaviour TargetPiece { get; }
         public Dictionary<SnapPoint, bool> AllowedSnapPoints { get; } = new Dictionary<SnapPoint, bool>();
 
         public SnapPointWhiteList(BuildingPieceBehaviour targetPiece)
         {
             TargetPiece = targetPiece;
             foreach (var snapPoint in targetPiece.GetComponentsInChildren<SnapPoint>())
             {
                 AllowedSnapPoints.Add(snapPoint, true);
             }
         }
     }

My custom editor script that I'm using:

  public class SnapPointInspector : Editor
     {
         private SnapPoint Target => (SnapPoint) target;
         private readonly Dictionary<int, bool> _foldouts = new Dictionary<int, bool>();
         private List<SnapPoint> _snapPointNames = new List<SnapPoint>();
 
         public override void OnInspectorGUI()
         {
             serializedObject.Update();
           
             GUILayout.Label("Allowed Snap Points");
           
             for (var i = 0; i < Target.SnapPointWhiteList.Count; i++)
             {
                 _snapPointNames = Target.SnapPointWhiteList[i].AllowedSnapPoints.Keys.ToList();
               
                 SetFoldout(i, EditorGUILayout.Foldout(GetFoldout(i), Target.SnapPointWhiteList[i].TargetPiece.GetBuildingPieceName(), true));
 
                 if (GetFoldout(i))
                 {
                     foreach (var snapPoint in _snapPointNames)
                     {
                         // GUILayout.Label(snapPoint.Key.name, EditorStyles.label, GUILayout.ExpandWidth(true));
                       
                         Target.SnapPointWhiteList[i].AllowedSnapPoints[snapPoint] =
                         GUILayout.Toggle(Target.SnapPointWhiteList[i].AllowedSnapPoints[snapPoint], snapPoint.name);
                     }
                   
                 }
             }
           
             HandleDragAndDrop();
             EditorUtility.SetDirty(target);
             serializedObject.ApplyModifiedProperties();
         }

And where it's getting saved in the HandleDragAndDrop() method:

  Target.SnapPointWhiteList.Add(new SnapPointWhiteList(draggedPiece));
                             EditorUtility.SetDirty(target);

I've also tried the serializedProperty route and had no luck there. When I edit the values in the editor nothing is persisting.