I do not "see" any of these options to del or remove the drives.
I have attached a screen shot HDToolbox. As per previous messages, I formatted a 300Gig drive into 7 active partitions. The "Ghost" drives I suspect have to do with perhaps "non-dos" areas of the drive ?
Unpartitioned areas of the drive will not show up as anything on Workbench. Only mounted partitions will appear on Workbench. Your NDOS? partitions must be ones without filesystems (correctly) installed, or they need formatting.
In the photo, the checkbox for 'Automatically mount this partition' is behind the Change button. So for each partition you'd want to hide you'd select the partition, then press the Change button, then untick the aforementioned checkbox.