Yes, I can perform a backup from the legacy version (but for how long?)
The new version (10) does, of course, allow backup, but only to Enex, and only notebook-by-notebook or 50 notes at a times. With scores of notebooks and thousands of notes, it is not feasible to have a backup that takes maybe ten minutes (as opposed to five seconds) to run.
Backupery is apparently an option, but it's not free. I'm loathe to pay for a workaround.