I was battling all yesterday trying to solve this. Still have no luck.
I’ve tried Rama’s Simulate Key Press but yeah does not simulate the actual keypress globally.
I also tried the Press Key (Widget Interaction Component) as it says "Press a key as if it had come from the keyboard. But no luck still.
I built a Macro in AutoHotkey that I am trying to fire from Unreal. All I want is Unreal to trigger this “L” hotkey from the keyboard 
@Packetdancer could you please elaborate on this SendInput idea? Would love to try it.