Modify scheduling on Azure WebJob
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.
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 it will 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)