Your example is trickier than some, but it’s okay once you break it down.
Grammatically, it’s a complex intransitive construction (S-P-PC) with the verb is followed by three coordinated predicative complements, each an NP, and where the final NP coordinate comprises a further coordination of two AdjPs modifying the noun:
Conformity is a [virtue], [creativity suspect], [humor forbidden and voice mute].
The nouns "virtue", "suspect" and "mute" are the heads of the three coordinated NPs.
The verb "be" is being used in its ascriptive sense, so that each coordinated NP is ascribing a property to the subject "conformity"