If you would like to remove the job from the Workshop calendar, you should start by unscheduling the job. To do this:
1) Click on the job and click Unschedule:
This will move the job out of the calendar and onto the Unscheduled Jobs list on the right.
2) You can now cancel the job in the Point of Sale. Follow the instructions here:
How do I cancel a customer order or quote?
After you have cancelled the job in the Point of Sale, it will disappear from the Workshop Module completely.
Please note that you cannot remove all items from a Workshop Job in the Workshop Module.