Hi there and best wishes for 2019,
Assuming the feature is net yet available in PRTG I would like to propose an additional channel setting for sensors, that if a sensor reports for a configurable time period a threshold state it's actually shown as warning or error.
Like for instance our database servers often show peak warnings and error states for CPU usage, and they usually disappear automatically after. And although it would be easy to monitor, it would be much more pleasant if we could say: "throw an alarm when cpu or memory usage is higher then xx% for a period longer than yy amount of time".
So we could see a sensor throwing an alarm or error state for a CPU threshold level on 95% for a duration of 15 minutes or longer.
Could this be something that would have take interest into implementing into PRTG?