What is the action you want to execute after the ley is held down for some time? You can use Tick, Gate and a float variable — add Delta seconds to the float on each tick and check if it’s more than, say, 3 seconds; and when the key is released — set float to 0;
Or upon presing the key start a Timeline with a curve that goes from 0 to 1 in 3 seconds, and check if the value is 1. The same curve may be used to drive some animation like a progress bar.