According to the CyberArk Defender PAM documentation, the Master Policy setting that must be active in order to have an account checked-out by one user for a pre-determined amount of time is Enforce check-in/check-out exclusive access. This setting enables organizations to permit users to check out a 'one-time' password and lock it so that no other users can retrieve it at the same time. After the user has used the password, the user checks the password back into the Vault. This ensures exclusive usage of the privileged account, enabling full control and tracking for the password. The duration of the check-out period can be configured in the platform settings for each account.Reference:

Account check-out and check-in - CyberArk

Master Policy - CyberArk