1. Go to Devices > Device Groups.
2. Click +Add.
3. Enter the attribute name in the Name field.
4. Click Dynamically Managed (Most Common).
5. Set a rule as All:
   1. Select "Custom Device Attribute" from the pop-up menu.
   2. Select the attribute name from the pop-up menu.
   3. Select "is equal to".
   4. Enter true as the value.
6. Click Save.