I know many people who hesitate about replacing Office simply because of the lack of an alternative for one note. Similarly I’ve noticed a few times when this issue has been raised on distro websites many people point to alternatives that are really not comparable (such as tomboy).
The one project I saw working towards this goal was Basket but sadly this project seems to have fallen into a development black hole. With that in mind (and with the existing possibilities of libreOffice) I could see it being the natural home for this type of program.