This is how you get thumbstick input on any actor that can receive input, for example on your player controller:
Also in player controller, create a dispatcher event with a float param and call it every frame on Tick whenever the value isn’t zero.
In your dialogue widget, subscribe to player controller’s dispatched event in OnInitialize.
On “Destruct” event, unsubscribe from it.
In your event that catches the float value in the dialogue widget, sum it up until a certain value is achieved. When it is, execute the logic that you see in OnKeyDown where it selects the next dialogue option either up or down.
Let me know how it goes or if you get stuck on anything.