Device Drivers are very flexible, and for that reason they are also very complex. In fact, creating device drivers is the most complex part in V-Control.
All available device drivers are stored as a template in a database (Devices.rsd). Once they're added to a project, a copy is stored in the project file (*.vc3) too. The Device Editor is used to modify / create these drivers. To modify a driver in an existing project file, the Device Editor is launched via Configure → Edit Devices. Now only devices in the current project are available for editing. This means also that all changes to the device driver concern only the current project. The device database with the templates stays untouched. To edit the device templates, the device editor is launched via Configure → Edit Device Templates. In this case, the drivers in the current project stay untouched.