Yes, that same setting I have on my Libra too. But on my Clara I see (under "Other Resources") the following (see attachment), which opens an about 77 page PDF.
I copied the found Kobo Libra manual as
userguide.pdf, into the .kobo/guide directory and now it shows up in the Libra too. So I assume it is an omission in the Libra FW distribution.
All Kobo user manuals can be obtained
here