AutoSave.cs

using System.Threading.Tasks;

using UnityEditor;
using UnityEngine;
using UnityEditor.SceneManagement;

[InitializeOnLoad]
public class AutoSave
{
    private static bool active = true;
    public static int Seconds = 10;

    [MenuItem ( "StartAutoSave", menuItem = "Tools/Start AutoSave.", priority = 10, validate = false )]
    public static async void Start ( )
    {
        active = true;

        while ( active )
        {
            await Task.Delay ( Seconds * 1_000 );
            Save ( );
        }
    }

    [MenuItem ( "StartAutoSave", menuItem = "Tools/Start AutoSave.", priority = 10, validate = true )]
    public static bool ValidateStart ( )
    {
        return ( !active );
    }

    [MenuItem ( "StopAutoSave", menuItem = "Tools/Stop AutoSave.", priority = 11, validate = false )]
    public static void Stop ( )
    {
        active = false;
    }

    [MenuItem ( "StopAutoSave", menuItem = "Tools/Stop AutoSave.", priority = 11, validate = true )]
    public static bool ValidateStop ( )
    {
        return ( active );
    }

    private static void Save ()
    {
        var saved = EditorSceneManager.SaveOpenScenes ( );
        Debug.LogWarning ( $"Open Scenes {( saved ? "" : "NOT " )}saved." );
    }
}