You can do this with the present notifications. Add a new custom alert, and pick then ‘Mains’ circuit. You can specify the kW you want to be notified of (can’t specify amps, but you can convert to kW). So for your example of 65% for a 200A service, 200A x 240V = 48kW x 0.65 = 31.2kW. You can spec an interval down to as low as 1 second.
There is also a built-in notification alert for when you hit a peak for the month also.
Also, you typically want to be looking at this in terms of power anyway. The Vue2 is and energy/power meter (kW and kWh), and not really a good current meter (A). Know that Emporia presently does not give you a true Amps value, it only records real power to the cloud. The Amps value shown is manufactured – the true Amps value (with no relationship to power factor) is not shared. This is a known limitation in their present implementation. Requests have been made to indicate current (A), Apparent Power (VA), and power factor – but unclear if this will ever be implemented.