I was lurking around, and I just found something not properly working on the documentation.
Nothing happens when you click on "backup folder".
When checked, the project will be saved periodically in the backup folder. For extremely large projects this may introduce unwanted pauses and can be disabled.
(I know I know, it's not as if my world depended on it, but hey, if I see something, it'd be better to tell it, isn't it?...)