These children's favorite indoor game is chess- what is the subject here
Identify the subject and predicate in the sentence These children's favorite indoor game is chess
These children's favorite indoor game is chess.
The subject is "these children's favorite indoor game", and the predicate is the verb phrase "is chess"
The copular verb "be" has the noun phrase "chess" as subject complement, so-called because it refers to the subject. In your example, the complement defines the childrens' favorite game as being chess.
The structure is thus S-V-C.