Keep pushing up to the category icons at the top of the screen, TV MOVIES and such and press enter on one, or wait a few seconds and it should swap to what you have selected. If you have multiple libraries built in a category, press up again and a secret menu is revealed which will bump the rest of your content down. Highlight your desired library and wait a second and it will change to it on the main screen or push enter to browse the entire library.
I don’t like the new way of browsing all libraries. I like the updated app and interface but I’d like to see Plex bring back the “Browse all” i.e. Movies, TV Shows on home.