I want to configure different threshold for different customised groups. eg. critical switches have a different threshold and non critical devices have different thresholds. and thresholds for everything ports, env, usages, reachability etc.
You can match on the device name using the SystemName property in the port/interface group ruleset. So, you could conceivably match on all of these device hostnames in a customized port group:
TrunkPort.SystemName equals "6500-1" OR
TrunkPort.SystemName equals "6500-2" OR