no built in way (besides waiting until the errors are older than your set time interval (30 days))
you *could* delete the task log index files, but i'd recommend against that, maybe you'll need them in the future to look something up
(in any case they are under /var/log/proxmox-backup/tasks/ )
proxmox-backup-manager node update --task-log-max-days 1
proxmox-backup-manager node update --delete task-log-max-days
you mean for pve?Is there a similar command for use on a node that is a member of a proxmox cluster (to clear the task log and cluster log)?
no there is nothing configurable, you're only chance is to delete the files by hand (or script). they are in /var/log/pveproxy (the access logs) and /var/log/pve/tasks (the task logs)