Totally understand - it is good to get a lay of the land. A lot that can be done with JavaScript.
One useful thing I see a lot of people use the Custom JavaScript for is Custom Footers, which can include social links and a “Back to Top” button (source).
Feel free to reach out further on the forum if you have any other questions or feedback. And whatever JS tweaks you do, we’d love to see them on the Share What You’re Working On topic (you can also get some interesting ideas there too, especially for JS).