We currently use the API below in an automation that creates a duplicate sheet of a template we created. All of the formatting and data is duplicated using the API, but updated Non-Working Days in the template is not making it's way into the new sheet.
Please include support for updated Non-Working Days data to passed via the API
Here is the current documentation for copying a Smartsheet.
https://developers.smartsheet.com/api/smartsheet/openapi/sheets/copy-sheet#/api/smartsheet/openapi/sheets/updatesheet