How they create Spam folder?

NextCloud 22
Mail App 1.10.2
IMAP server Dovecot 2.3.15

In this article 5 open source webmail clients for browser-based email | Opensource.com in NextCloud Mail app screenshot there is a Spam folder.
How they create it?

gmail-nextcloud

All that I can get only two ā€˜Junkā€™ folders.
Canā€™t create Spam folder as submailbox.
App with any problem allows to create submailbox with any name instead of ā€˜Spamā€™.
With this name it throws no error, just didā€™t create anything.
Also canā€™t rename existing Junk folder to Spam.

So how they create Spam folder on those screenshot?

Part of Mailbox Dovecot config

 mailbox Spam {
    auto = subscribe
    special_use = \Junk
    autoexpunge = 7d
 }

 mailbox Junk {
    auto = subscribe
    special_use = \Junk
    autoexpunge = 7d
 }

Well you can create the mailbox. And Mail will try to guess itā€™s special use. If the mailbox has \Junk set by the server then it will show as a special spam mailbox. Nevertheless there currently is no way of setting a spam mailbox. This is missing, as we just found out the other week: Move spam messages to spam mailbox Ā· Issue #5326 Ā· nextcloud/mail Ā· GitHub