Modify scheduling on Azure WebJob
To change the schedule, or to Modify the CRON value just use the App Service Editor to modify the WWWROOT/App_Data/jobs/triggered/YOUR_WEBJOB_NAME/settings.job file;
By the time of writing, App Service Editor is still in preview but itwill work.
In the settings.job file amend the schedule in CRON value and will be reflected in the App's Web Job Dashboard.
The App Service Editor is available in App Service > Development Tools
App Service Editor (Preview)
I finally found it.Scheduled WebJobs turn up under Scheduler in the main bar.
The Save button is not visible until you actually make a change.