A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
I have the exact same issue after this last Microsoft Update. However, the pinned list shows up if you open, say excel, and once it opens, right click on excel in the taskbar and the pinned items show up. This is the same for word as well. Why it got removed from the start menu right click, your guess is as good as mine. I haven't found an answer for it yet.
As far as trying to pin items back to the start menu app, there is no option to do that. Even after manually opening several files, none of them show up like they used to in the start menu. Only when you right click on the app in the taskbar does the pinned and MRU list appear.
Hopefully someone will find a fix for it or Microsoft can fix their update that they pushed causing this.