How to show <ol> hidden by default?

Hello guys this is my question:
when I try to read a book at the bottom of the page there is link “site index”.
When I click on it the broswer open a page with a list of chapters about the book.
This list is an “ol” full of “li” elements but it’s hidden by default. If you click on the button “+” it shows the “ol”. I’d like to keep the functionality of the botton but I need to have the “ol” visible by default. How can I do this? I need to change my javascript file or the css file? I add a picture (I can only add one) to explain better my problem. Thanks!

You’d need to do some javascript hacking – there’s no setting that will make that happen by default, that I know of.