Make sure you get the specific actor in the level that has the variable you want to change, and then its subcomponent.
If you only have one actor of that class in your level, use a Get All Actors Of Class node, followed by an Array Get node (value “0”). That gives you a single Actor output pin with access to that specific actor’s functions and variables.
You can probably connect that to a “Set Trace Length (HoverComponent)” node through the context menu, or first get the Hovercomponent and then set that variable.