I have two questions.

First, what is the name of the function that computes other functions
"indirectly"?

As I recall, it is something like SUBFUNCTION(funcNumber, funcArgs).
Obviously, SUBFUNCTION is the wrong name.

Second, how can I get a comprehensive list of Excel functions using
Excel Help (perhaps), either alphabetically or by category?

I know that if I enter a "similar" function name in Excel Help, Show
All gives me the option of getting a list of related functions in a
category. But I was unable to think of a function similar to what I
call SUBFUNCTION. I would have been content with exhaustively
searching a list of all Excel functions. But I was unable to get that
comprehensive list.