Where should I see Delete Entire Mailbox button?

SYSTEM INFORMATION
OS type and version CentOS Linux 7.8.2003
Webmin version 1.981
Usermin version 1.860

I set Show button to delete entire mailbox? to yes and saved, but I don’t see that button anywhere in my inbox or manage folders. I’m trying to delete invalid emails, similar to closed topic Usermin - Webmail. I have about 60 invalid emails (sender none, subject (no subject), date 12/31/1969) that defy all efforts to exterminate them.