You can get the streaming level name in blueprints fairly easily.
Do a MultiLineTraceByChannel from the ActorLocation of the player.
Do a ForLoopWithBreak to loop through the hit array. Break the ArrayElement HitResult and cast the HitActor to LandscapeStreamingProxy - when you find a LandscapeStreamingProxy break from the loop.
On the LandscapeStreamingProxy call GetPathName - this returns the complete path to the LandscapeStreamingProxy.
If you examine the path in debug you can see how to Parse the string into an Array with ParseIntoArray. Have CullEmptyStrings ticked.
Selecting the right array element and successive calls to ParseIntoArray will allow you to whittle down the string until you get the actual Streaming Level Name.