Bookmarks allow you to save your favorite pages in one easily accessible location. Unlike pinning, your bookmarks are only visible to yourself; no other teammates can view or edit them. If you find yourself returning to a page time and time again, save yourself the hassle by bookmarking it.
Navigate to the category or page, click the kebab menu (three vertical dots) next to the name of the page, and select "Bookmark":
When you bookmark the page, it will appear in left hand sidebar:
If you need to remove a bookmark for any reason, navigate to the page, click the kebab menu, and select "Remove bookmark".