Unity custom editor from drag and drop to change the size of an area

WorldSectionInitializerEntity.cs

using ProjectEdg.CoreModule;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Tilemaps;

namespace ProjectEdg.WorldModule {
  [ExecuteInEditMode]
  public class WorldSectionInitializerEntity : MonoBehaviour {
    // other code
    
    public void ForceDrawGizmos() {
      _cachedDrawControlledArea = _drawControlledArea;
      _drawControlledArea = true;
    }

    public void RestoreDrawGizmos() {
      _drawControlledArea = _cachedDrawControlledArea;
    }
    
    // other code
  }
}

WorldSectionInitializerEntityEditor.cs

using ProjectEdg.CoreModule;
using ProjectEdg.EditorTools;
using UnityEditor;
using UnityEngine;

namespace ProjectEdg.WorldModule {
  [CustomEditor(typeof(WorldSectionInitializerEntity))]
  public class WorldSectionInitializerEntityEditor : FoldoutGroupEditor {
    private const float HANDLE_SIZE = 0.2f;

    private void OnSceneGUI() {
      var worldSectionInitializerEntity = (WorldSectionInitializerEntity)target;
      var position = VectorUtility.Floor(worldSectionInitializerEntity.transform.position);

      EditorGUI.BeginChangeCheck();

      // create a single handle in the top-right corner to manage the size of the world section area
      var cornerHandle = position + new Vector3(
        worldSectionInitializerEntity.Size.x + (HANDLE_SIZE / 2),
        worldSectionInitializerEntity.Size.y + (HANDLE_SIZE / 2),
        0f
      );

      // we need to cache this value to be able to determine if the hot control changed this frame in order to
      // detect the click / release of said hot control since Handles.FreeMoveHandle will modify this value during
      // the same frame
      var hotControlId = GUIUtility.hotControl;

      Handles.color = Color.yellow;

      var handleControlId = GUIUtility.GetControlID(FocusType.Passive);
      var newCornerPosition = Handles.FreeMoveHandle(
        handleControlId,
        cornerHandle,
        HANDLE_SIZE,
        Vector3.zero,
        Handles.DotHandleCap
      );

      if (EditorToolsUtility.WasControlClicked(handleControlId, hotControlId)) {
        worldSectionInitializerEntity.ForceDrawGizmos();
      }

      if (EditorToolsUtility.WasControlReleased(handleControlId, hotControlId)) {
        worldSectionInitializerEntity.RestoreDrawGizmos();
      }

      if (EditorGUI.EndChangeCheck()) {
        Undo.RecordObject(worldSectionInitializerEntity, "modify world section initializer controlled area size");

        var newSize = worldSectionInitializerEntity.Size;
        newSize.x = Mathf.FloorToInt(Mathf.Max(1f, (newCornerPosition - position).x));
        newSize.y = Mathf.FloorToInt(Mathf.Max(1f, (newCornerPosition - position).y));

        worldSectionInitializerEntity.Size = newSize;
        EditorUtility.SetDirty(worldSectionInitializerEntity);
      }
    }
  }
}