If you make the tray wider, the symbols will appear larger. Or you could remake the scrapbook using fewer columns of symbols.
Some folks place commonly use symbols and other entities in the gray space outside of the paper. They can make them as large as they want and the copy and drag them into place in the paper space. The entities become part of the template so they show every time the template is used.
If you have commonly used line styles or text sizes, you can put samples of them outside the paper space, too. then you can sample them when you want to use them.