概要

using System.Linq;
using UnityEditor;
using UnityEditorInternal;
using UnityEngine;

public class Example : ScriptableObject
{
    public int    m_id   = 25;
    public string m_name = "ピカチュウ";

    [MenuItem( "Tools/Save" )]
    private static void Save()
    {
        var example = CreateInstance<Example>();

        InternalEditorUtility.SaveToSerializedFileAndForget
        (
            obj: new Object[] { example },
            path: "Assets/Example.yaml",
            allowTextSerialization: true
        );

        AssetDatabase.Refresh();
    }

    [MenuItem( "Tools/Load" )]
    private static void Load()
    {
        var path = "Assets/Example.yaml";
        var list = InternalEditorUtility.LoadSerializedFileAndForget( path );

        var example = list
                .OfType<Example>()
                .FirstOrDefault()
            ;

        Debug.Log( example.m_id );
        Debug.Log( example.m_name );
    }
}

InternalEditorUtility.SaveToSerializedFileAndForget で保存、
InternalEditorUtility.LoadSerializedFileAndForget で読み込みが可能