I want to be able to visualize where my ‘ResourceAreas’ are whilst in edit mode so i tried to create a tool to display them in the scene view. Here is the code for the editor:

using UnityEngine;
using UnityEditor;

[CustomEditor(typeof(ResourceAreas))]
public class ResourceAreasEditor : Editor
{
    void OnSceneGUI()
    {
        ResourceAreas resourceAreas = (ResourceAreas)target;

        foreach (ResourceArea area in resourceAreas.resourceAreas)
        {
            Handles.color = Color.red;
            Handles.DrawWireDisc(area.center, new Vector3(0,1,0), area.radius);

            EditorGUI.BeginChangeCheck();
            Vector3 newCenter = Handles.PositionHandle(area.center, Quaternion.identity);
            if (EditorGUI.EndChangeCheck())
            {
                Undo.RecordObject(resourceAreas, "Move Resource Area Center");
                area.center = newCenter;
                EditorUtility.SetDirty(resourceAreas);
            }
        }
    }
}

However upon selecting my ResourceAreas scriptable object no discs appear in the scene view. This is the code for the scriptable object and what one looks like in inspector:

using UnityEngine;

[System.Serializable]
public class ResourceArea
{
    public string resourceName;
    public Vector3 center;  // Center point in terrain space
    public float radius;    // Radius of the resource area
    public int resourceCount;
}

[CreateAssetMenu(fileName = "ResourceAreas", menuName = "ScriptableObjects/ResourceAreas", order = 1)]
public class ResourceAreas : ScriptableObject
{
    public ResourceArea[] resourceAreas;
}