[imp] config Show All Mailboxes

[Server Admin]

Excuse me for reposting this but it looks like it’s lost in a previous weeks archive.
I’m running Horde email application under cPanel for my users.
cPanel upgraded the version of Horde that ships with it recently and many defaults have disappeared.
The screen indicates horde Groupware 5.1.1

I have searched the archives in various places and only find really old answers to this.

How can I set the default to “Show All Mailboxes” after a user logs in?

I tried editing the prefs.php

prefs.php

$_prefs['nav_expanded'] = array(
    'value' => 1,
    'type' => 'enum',
    'enum' => array(
        0 => _("No"),
        1 => _("Yes"),
        2 => _("Remember the last view")
    ),
    'desc' => _("Expand the entire folder tree by default in the folders view?"),
    'suppress' => function() {
        return !$GLOBALS['injector']->getInstance('IMP_Imap')->access(IMP_Imap::ACCESS_FOLDERS);
    }
);



But this doesn’t seem to solve the issue.