Is there any way to heal a umbilical hernia without surgery?

No: Hernias exist because the herniated material has slipped through a hole in the tissues that should hold it back. These tissues have a minimal blood supply and the herniation, even when episodic, separates the tissues so they could never heal on their own. Some hernias don't produce enough symptoms or risk of complications to require surgery, but many do.

Generally not: Except infants in whom it may regress as gets older. In adults / older children generally repair but if not fit for operations then can watchfully wait and urgent attention if severe pain cat reduce or vomiting. Hernia belts controversial and some say more harm than good

Not really: Some people will use a pressure belt to help them manage symptoms from a hernia but these are more commonly used for hernias in the groin and they are not particularly effective. The surgery for an umbilical hernia is usually considered a fairly minor day procedure - not something to worry too much about.