@{
    var templates = new List<object>();
    var templateNames = new[] { "Invoice", "Receipt", "Shipping Label" };
    foreach (var name in templateNames)
    {
        templates.Add(new
        {
            name = name,
            html = $"<h2>{name}</h2><p>Dynamic content...</p>"
        });
    }
    var htmlTemplatesJson = JsonSerializer.Serialize(templates);
}

<richtextbox
    name="dynamicTemplatesEditor"
    toolbar="full"
    height="400px"
    html-templates-json="@htmlTemplatesJson" />