I have made a minimal example showing what I am describing. You can find the example here.
In this example, the Level Blueprint will, every second, increment a local variable, starting from 0. After the increment, the Level Blueprint will set this variable in the BP_GameState. The Game State will do nothing with it, it will only store it. I placed in the world a blueprint called BP_SomeActor. This actor has a TextRender component. On the Tick event, this actor will read the variable from the BP_GameState and will set this value as the text in the TextRender. This is how you can “read” a value from the level blueprint. You cannot read it directly, but you can one the Game State to store any value you want actors to be able to access.