Is there any REST API or dedicated azure CLI commands that can help in the deployment of the workbook. Workbook deployment mentions ARM deployment, but maintaining a huge "serializedData" in the arm template is nowhere practical.
I am not aware of any CLI command for workbook deployment. One easy workaround to your problem is to add a parameter in the ARM template for the serialized data instead of maintaining that in the template itself. Then you can just do a regular az deployment using the template and pass your ARM parameter from outside.