I got the basic synchronization to work on my glo (firmware 2.3.0) but can't see them in my library :
On first sync, only an empty directory "dict" was created on the Google drive (inside the "koboExt" directory). This remained the same after a few sync attempts.
Then I put two epubs from my computer to the Google drive, and after sync, the files appeared on the glo Filesystem. The only thing is that they don't go into the books or the library list...