Directional light is placed in the
level
In case you ever revisit this topic in search for more answers.
Consider using [Event Dispatchers][1] for this, it’s one of the methods to communicate with the Level Blueprint. It does take some time to wrap one’s head around, though.
The most straightforward use scenario would look something like this:
Create a dispatcher In the Player Character (you can send any type of data this way):
In the widget, you get access to the Player Character and call the dispatcher (Call ED_AdjustLight sending a float value)
In the Level Blueprint you bind the dispatcher to any Custom Event you desire (and you automatically get access to the data you sent):
Now, whenever you use a slider in the widget (pic 2), it asks the Player Character to dispatch a request. If anyone is listening to this request (and the Level Blueprint has a registered custom event just for that), the data will be sent to the Level Blueprint.