Minecraft wiki entry for scoreboard, associated text: Syntax
scoreboard objectives list
Description
List all existing objectives with their display names and criteria.
Result
Command Trigger Java Edition Bedrock Edition
... list there's no objective in scoreboard system Successful Failed
On success List all existing objectives.
Output
Command Edition Situation Success Count /execute store success ... /execute store result ...
... list Java Edition On success 1 1 the number of objectives in scoreboard system
Bedrock Edition On fail 0 N/A N/A
On success the number of objectives in scoreboard system N/A N/A