On my understanding, you want to use two fonts: One exclusively for the title screen and another one for the rest of the things on the game.
The first font on the plugin parameters is the default font for all things.
So, let the first font be your default. You don't need to assign any window or scene into it. If it is the first, it will be the default for all.
Now, on your second font, apply that exclusively for the Title Screen. If you want to change the font for all things on the title screen, just apply it into the Scene_Title. If you want just for the Game Title, apply it just for it.