in order to get data from a level the level needs to be loaded. (full stop)
now that being the case you might be trying to over think this. instead of trying to get the data from the level, could you get the data from say the game mode, or the specific serialized save file instead?
in your “main menu” level you can go get the Serialized Save files, and then read from those, that way you don’t need to load the level to get the data, because there is the chance that you might be loading something rather large, or drastically different to the Main Menu screen.