Hi Nastaran,
Thanks for contacting Syncfusion support.
We assume that your requirement to “update the nodes in diagram when changes happened to its respective symbol in symbol palette”. If so, we don’t have an option to change the appearance of nodes/connectors at runtime for symbol palette items. In symbol palette, you can add/remove symbols(node/connector) to palette using addPaletteItem and removePaletteItem method respectively.
Please refer to the help documentation for adding and removing symbols at run time.
Regards,
Ramya T