Drag-dropping M4R Ringtone to iTunes 12.0.1 to appear in iTunes ringtone folder?
I just tested and the process worked correctly in iTunes 12.0.1. However, I did initially encounter an issue when I tried to add a file that had the same name and was the same size as a song already in my iTunes Library.

Here are the steps I followed:


I dragged-and-dropped MyFile.mp3 into iTunes.
I right-clicked on it and chose "Create AAC Version".
I right-clicked on the AAC version and chose "Show in Finder".
I dragged-and-dropped the AAC version onto my desktop, creating a copy.
I renamed the file on my desktop to MyFile.m4r.
I dragged-and-dropped the file back into iTunes. This didn't do anything. However, having read that iTunes sometimes refuses to import files like this, since it thinks they are identical, I removed the AAC version from iTunes.
I again dragged-and-dropped the m4r version into iTunes, and this time it showed up in the Tones section of the Library correctly.