Sometimes you need to write down new task quickly. Or split a bigger task you're working on into a few small tasks - that really helps.
Actually, if you don't need complex tasks managers, you can use SideNotes only. It just works.
To add task just press ⌘T and the current line will become a task: a checkmark will be placed in the line beginning. If you press the mentioned shortcut again, the checkmark will disappear. You can do it also by clicking the text formatting button.
Pro tip. You can add tasks even quicker. A checkmark is actually saved as
[ ], if it's not checked, or
[x] if it's checked. So if you write
you can place a checkmark wherever you want.