Back to the question raised in the OP. For me I like to keep my secret phrases or passwords on a booklet containing other valuable articles and write-ups. Writing it on a booklet or two booklets as a way of duplicating them helps much. Copying passphrases/passwords online or storing them on the cloud or emails is a no-no for me. I like to keep it simple. Don't use a distinct booklet. Let it be on a booklet that won't trigger scrutiny of preying eyes. Then, sensibly leave the booklet at a place that won't make it look like you're hiding anything. After all, they say the best way to hide something is to expose it.