You can watch a video presenting this tip here.
You can use SideNotes for keeping text snippets. It’s super useful if you need to use the same piece of text many times. For example, you can make a note with your address, important numbers or your email signature.
Now you can quickly find it using the Search window which you access using a global shortcut.
Once you find the snippet you're looking for, simply press ⌘C to copy its content. If you press ⌘⌥C, it will copy everything but the first line, so you can use the first line for a title and put actual content below it. Once you press it, the Search window disappears and the last app you were using will be back in front, so you can paste the copied text.