There is two sets of manuals, the regulatory one being the approved flight manual (AFM), and the suggested procedures these being in a pilot operating handbook or Fcom.
The AFM is a much smaller document be it for a Boeing or a Cessna that cannot be varied..
Pilot operating handbooks or FCOM contain generic techniques which expand on the AFM can and should be modified when local situations deem it necessary without modifying the core AFM requirements which are a subset.