public string Description {get; set;}

var table = MapView.Active.Map.GetStandaloneTablesAsFlattenedList().FirstOrDefault();
if (table == null)
  return;
QueuedTask.Run(() =>
{
  var tableTemplate = table.GetTemplate("Template1");
  
  var definition = tableTemplate.GetDefinition();
  definition.Description = "New definition";
  definition.Name = "New name";
  //Create new table template using this definition
  table.CreateTemplate(definition);

  //You can also create a new table template using this extension method. You can use this method the same way you use the layer.CreateTemplate method.
  table.CreateTemplate("New template name", "Template description", tags: new string[] { "tag 1", "tag 2" });
});

QueuedTask.Run(() =>
{
  var tableTemplate = table.GetTemplate("Template1");

  var definition = tableTemplate.GetDefinition();
  definition.Description = "New definition";
  definition.Name = "New name";
  // update the definition
  tableTemplate.SetDefinition(definition);
});