Workorders should never be deleted. To do so breaks the continuity of the numbering system, and also is a "red flag" in an audit. It signals "missing workorders" and "hidden income."
If work is not completed on an Estimate, it should be noted and then closed, using the 
option in the Workorder Screen. This provides a positive audit trail of all customers, work that is completed, or not, and the reasons. It also satisfies accountability in an audit.
With this said, on the main workorder display screen, you do have a 
button that will remove workorders. Although we do not believe it is a good business practice, some clients do want this feature. Pressing the button will remove the workorder record.