How to make the sheet not cleared at startup?

Question

Unity

Like there is a sheet:

[System.Serializable]
public static class GridActions
{
    [SerializeField] public static List<Cell> AllCell = new List<Cell>();
}

It is filled like this:

GridActions.AllCell.Add(cell);

After filling (through the code). I check the content without running.

[ContextMenu("Test")]
    public void Check()
    {
        GridActions.AllCell.ForEach(cell => print(cell.name));
    }

Everything is fine without starting. It's full.

Then I launch and the sheet is empty (nothing came up). I turn it off, I try to start it and it does not display anything. The sheet is cleared on startup. How to fix?