You can watch a video presenting this tip here.
SideNotes allows you to move notes to other folders or to rearrange notes within a folder. To move them up or down, simply drag a note by its bottom area (see the screenshot below) and drop it in the desired place.
You can do it also using a keyboard shortcut: ⇧⌥⌘↑ (moves up)
and ⇧⌥⌘↓ (moves down).
For all keyboard shortcuts, please visit Keyboard Shortcuts article.