how to setup the folder separator a "/ " instead of a dot "." in imap maildir postfix and dovecot

Question

The Question is already in the title. I want to setup dovecot and postfix with maildir , but I do not want the dot "." as folder separator. I like to use a folder system like "/"

Maildir/folder/
Maildir/folder/subfolder/

I found this : https://doc.dovecot.org/configuration_manual/mail_location/Maildir/

mail_location = maildir:~/Maildir:LAYOUT=fs

I also setup the Namespace Inbox accordingly

mail_location = maildir:~/Maildir:LAYOUT=fs
namespace {
  inbox = yes
  prefix = INBOX/
  separator = /
  subscriptions = no
}

I used this setting but dovecot still using the dot. Does somebody here have another idea? Is theree some other setting that I ignored?