How to hide unknown devices in Dell OpenManage Essentials (or IT Assistant)

When discovering a large number of devices, usually you'll pick up a few non-Dell bits of hardware, such as Virtual Machines or network switches.

Luckily Dell have an option to avoid cluttering up OME with these, although of course they have put it in a wierd place.

Instead of being with all the main configuration options under preferences, it's actually under the discovery schedule settings in Manage / Discovery and Inventory / Discovery Schedule