No, indeed none of the post Opera 12 have a NOTES tab. Please bring it back.
My Notes files is actually a large collection of media articles from the internet, each note therefore being between 500 and 3000 bytes in size. So: being grouped by category and subcategory, which naturally alter as more are added, I move them around. In the Notes folder, it is easy to move and regroup them, much, much easier than in a Word file.
A text-based structure of this sort is far easier to use than Word, etc, notwithstanding no images. Life is possible without them, or one can use an appropriate programme.
And that's not all! Unlike most users, bookmarks are of absolutely no value whatever to me. Indeed, bookmarks' only value is that up to about Opera 9.27, one could copy between Notes and Bookmarks, which is much more precise and reliable than importing. A very useful function, since lost.
So I am still using 9.27 for note manipulation and 12.15 for browsing. (FYI XP SP3, Pentium 4 3GHz, 2GB). It is the mark of a good product that the older versions still work well.