Is the following sentence okay? Some Asian materials have sentences such as:
The guests were served caviar, truffles and foie gras, much more usual steak.
Presumably, they consider "much more" to be the positive version of "much less."
No, the sentence is not okay. "Much more" is not used that way.
As you say, a better phrase would be "not to mention..." or "as well as..." or "plus, of course,..." or (less strongly) "in addition to...."
In addition, the "not to be mentioned" thing takes the definite article:
The guests were served caviar, truffles and foie gras, as well as the usual steak.