As you start to get create and open more notebooks you might have a cluttered navigation bar on the left, something like this:
If this is the case for you I have a tip for you: rename your notebooks to something shorter. You can right-click on a notebook and choose Rename, then you can choose a shorter name for your notebooks and you can view more of them on your navigation bar. See what this looks like afterwards:
Works great for me, you should try it out but results will vary depending on your screen resolution.