Depending on what exactly you want the notes for ...

You can double click most data fields and get that little detail worksheet.  Anything you write on the left side will carryover to next year.  And because those notes from the left side are carried over, the data field in the next year shows zero, rather than being blank, so that can alert you that there is a note about that item.

Again, that won't solve all things that you need a note for, but it may help with some line-specific notes.