While it isn’t an Unbounce page builder feature, if you’re using Chrome as your browser, you can zoom in and out of the browser tab by pressing Ctrl + (- or +) or _ + (- or +).

Hi - that makes everything on the screen smaller/larger but does not display any additional parts of the actual landing page. Sometimes I do longer form pages, and it is awkward to move portions around if I don’t have more visibility.