Need help in leveraging MySQL auditing
Assuming you can find a way for your monitoring software to use an actual account, and further assuming your list of trusted/non-audited users is more static, then using the "exclude user" options should mean less maintenance.

To exclude a list of trusted users from being logged, the MariaDB audit plugin has a server_audit_excl_users option, and similarly the Percona audit log plugin has a audit_log_exclude_accounts. 

BTW, regarding rotating users/passwords, you might be interested to know that MariaDB 10.4+ has an expiring password feature.