Which of the following is a correct action taken as noted on the Libero control sheet?

The correct action taken as noted on the Libero control sheet involves identifying and tracking the substitutions and roles of the players specifically regarding the Libero. In the scenario where #6 substitutes for #1, this indicates a proper adherence to volleyball substitution rules and the designated role of the Libero, whose primary responsibility is to replace a back-row player. This action is clearly documented on the Libero control sheet, as it reflects a player's identification, club regulations, and game strategy involving the Libero’s critical function in enhancing team performance.

The other options do not accurately represent the intended actions on the Libero control sheet pertaining to proper substitution procedures. For instance, the mention of a Libero replacing another Libero or a player serving in a specific position pertains more to tracking general rotation and player positions rather than the specific role and actions of the Libero. Understanding these distinctions is essential in both managing the game effectively and adhering to the procedural rules set forth by governing volleyball authorities.