Landing with QFE - how to set the press. controller?

[Whatsit Doingnow]

To answer the question from the OP, I don't know about other aircraft but from the 737 FCOM, the last item for QFE Operation supp procedures is:

Landing altitude indicator ............ Set at zero

And whilst we're on the subject, can someone please explain to me the reason for this:

Note:

Do not use LNAV or VNAV below transition altitude/level.
Altitudes in the navigation data base are not referenced to QFE.

Use only raw data for navigation.

I can understand why they say don't use VNAV, but why not LNAV?