1. Add the plugin (administration –> plugins management –> search and install) Indexmenu Plugin (of Samuele Tognini).
2. create a page named “sidebar”. This will activate the sidebar that is already present by default.
3. In this page “sidebar”, enter {{indexmenu>accueil_welcome#1|js navbar }} as content (adapt the name of your folder!).

Go to administration –> parameters of template –> brightness of the page (130em) and brightness of the sidebar (25).

In a console of the Nethserver: edit /usr/share/dokuwiki/inc/pageutils.php and comment out the line $id=utf8_strtolower($id); with /* and */

# cd /usr/share/dokuwiki/inc/
# cp pageutils.php pageutils.php.orig
# nano pageutils.php

In a console of the Nethserver: edit /usr/share/dokuwiki/lib/plugins/config/settings/extra.class.php and add a “space” (=blank) between the “.” and the “ ' ” in $str = '_-.'; in the function __construct($key,$param=null) (a few lines after “Class setting_sepchar”):

# cd /usr/share/dokuwiki/lib/plugins/config/settings/
# cp extra.class.php extra.class.php.orig
# nano extra.class.php
       -->  $str = '_-. ';

In Dokuwiki, login as admin and go to “administration” –> “parameters” and search for “sepchar”.

Then choose the space (“ ”) instead of the “_”.

Don't forget to backup /etc/dokuwiki, /var/lib/dokuwiki, /usr/share/dokuwiki/inc/pageutils.php and /usr/share/dokuwiki/lib/plugins/config/settings/extra.class.php

After an update of dokuwiki by updating the module(nethserver-dokuwiki), the above described settings about the “spaces” and the capital letters into the page names must be redone (because updating the rpm over-write the files).
The plugin for the index menu (see 1.) must be re-installed.