Four mess stewards are listed for the engineering department, and I think some for the "glory hole", as well. Did the engineering personnel have their own stewards?
"Glory hole" was a pejorative term for the stewards accommodation which became legitimised in the administrative documentation. The Glory Hole Stewards, rated as such, were responsible for the security, cleanliness and good order of the stewards' accommodation.
This included such essential duties as securing (port deadlights) for heavy weather or ice warnings. They habitually performed other services for the stewards on a gratuity basis, such as bedmaking. They also formed a pool of labour for extraneous duties such as rigging up the public rooms for passenger entertainments etc. Glory hole stewards had little professional 'finesse' as you can imagine and were at the bottom of the hierarchy in status.
Apart from boy ratings such as bell boys and pantry boys, then would come engineers' stewards, considered somewhat inferior to officers' stewards.
On the passenger side there were utility stewards (scullions etc.) stairhead stewards, dining room (saloon) stewards, bedroom stewards and public room stewards. The captain's steward would be in there somewhere depending on his age and experience.
This hierarchy was neither official nor fixed although it was reflected in the wage scales to a great extent. It would furthermore be obfuscated in large passenger vessels by the passenger class divisions, particularly in regard to the public room stewards. The first class public room stewards were generally acknowledged to be at the top of the heap and were colloquially referred to as "topside" stewards or "topsiders".
My exposition here is by no means complete and does not touch upon the considerable pantry and kitchen staff, specialist ratings such as head waiter or those with officer status such as the Chief Steward's staff. Nor have I attempted to make it specific to Olympic/Titanic.
In general, catering manning varied between companies and was influenced to some extent by union negotiation.
As I've said elsewhere, if you are now suitably confused you would not be alone!