Unfortunately, you can't change the shifted version of a key with Bazecor; what Shift does to a key is determined by your computer's input language.
However, you can set up a key behavior that produces different symbols from a key with and without Shift (or other modifiers such as Alt), but for that, you have to edit the keyboard layout at the OS Level.
On Windows, there is a program called "Microsoft Keyboard Layout Creator"; on macOS, there is a similar program called "Ukulele". Those will allow you to customize the shifted version of a key, but it will only work on the computer where you have installed that modified layout.
You can learn more about how Bazecor and input languages interact in this video: