Sure. You first need to configure one of the customizable groups to match the desired devices. Then, you can re-prioritize that group so that DFM matches the devices using that group before one of the system-defined groups. Then you can modify the thresholds for the customizable group.

To edit a customizable group, go to DFM > Configuration > Other Configurations > Group Administration. The re-prioritization and threshold modifications can be done under DFM > configuration > Polling and Thresholds.