hmmm well thats an issue. the level bp is notoriously difficult to get a reference to in blueprints. what is the context of this widget going to be? like will it be something that will always be present during play? im assume so given the way you create it. if thats the case then you may want to create the widget elsewhere where it will be easier to reference, such places could be in the character bp, the game mode, or the hud class.
also note that in the picture you show a get node plugging into the add to viewport node, this get is redundant since your already getting the value from the set node.