The Delete action in Sales Order is not showing causing the Administrator having no option to delete a sales order.
Standard Sales Order comes with the standard Delete action. The common situation why Delete action is not showing is because the Sales Order form is a customized one and the Delete action is set not show.
To show the Delete button, the customized Sales Order form must be edited. To do this:
1. Navigate to Customization > Forms > Transaction Forms > Edit the Sales Order form.
2. Navigate to Actions tab > Standard Actions subtab > Delete > Check the box under Show column.
3. Click Save.