You’re likely looking at the wrong menu. There are 2 categories of menus in PT9. There is one Main Menu, which is in the upper left of the entire PT program is likely what you’ve been looking at.
Each tab or window then has a Project Menu in the upper left of just that window. It’s under this list where you’ll find the Notes option.
Splitting up the menus is extremely helpful. In particular, the Project Menu customizes itself to only show options that work for that particular kind of window. So you won’t usually see grayed out options which are only applicable to other styles of windows.