If you want to adjust evaluation weights with Sayulisp, you can use 'Tools/SayulispEditor/sayulisp-editor.py'. (required Python3 and its Tkinter)
If you have done adjusting them and created the script file, then you can run Sayuri with the following command.
sayuri --sayulisp <script file path>
If you want to change source code of Sayuri, you can do what you want.
But I don't merge your changes into my GitHub repository.