mmmm, when using the notes for the PO, and you add a new note, the top of the note window, there is a printer icon and a folder icon. the folder icon is where you can copy notes from a text file.
this might be the viable solution, for then you could save your different notes that represent the topic you want to copy in.  or you can just use the copy /paste within windows.
i don't see any mechanism to copy from another PO.