When we should use Credential Pool with multiple credentials?
A Credential Pool is a collection of credentials. Some external systems(target) allow only one active session per user at a time. For such external systems, a Credential Pool can be created, that would hold all the available credentials for that external
System. Each workflow instance acquires a single credential from a pool at any given time. Hence, if a user wants to run multiple Workflow instances the user can acquire multiple credentials from a credential pool.
Note: If a credential belongs to a Credential Pool it cannot be used in a workflow directly, it can be used via pool only.