Hello Anton_Edlund,
By default Save As action you need to modify.
Copy the ""Save Workbook As"" action and create duplicate of it.
Replace wb.save(filename) to below code
wb.SaveAs(filename, 51, System.Reflection.Missing.Value,
System.Reflection.Missing.Value, false, false, 1,1, true,
System.Reflection.Missing.Value, System.Reflection.Missing.Value, System.Reflection.Missing.Value)
Publish the action and use. while passing the parameter to the action under filename parameter, please mention the filepath with xlsx extension.
Hope it will help you.
Thank you.
Regards,
Vijay Rudrappa Dodamani