SideNotes shows and hides instantly. There are three ways to do so. Choose the one that is most convenient for you: Open Bar, Hot Side and Menubar Icon. The first one uses Open Bar – a small vertical, semitransparent button on the right (or left) side of your screen. You can click it to show your notes. If you choose Hot Side option, just move your cursor to the edge of your screen (there’s no vertical button). The third option is a Menubar icon: once you click it, the app appears. Click again and it disappears. Simple.
To activate the Menubar Icon, go to Preferences and set Show or Hide Notes to Menubar Icon.