Of course I did. Didn't forget to edit the text I copied, sorry. In my files my action is called the same as my file name.
// Eigene Button für die Community.
'start' => array(
'title' => 'Community',
'data-icon' => '',
'href' => $scripturl . '?action=start',
'show' => true,
'sub_buttons' => array(
'shoping' => array(
'title' => 'Shops',
'show' => true,
'sub_buttons' => array(
'shop1' => array(
'title' => 'Amazon-Partnerlink',
'href' => 'http://www.amazon.de/?&tag=diehybrpilo-21',
'target' => '_blank',
'show' => true,
),
'shop2' => array(
'title' => 'Shirtinator-Shop',
'href' => 'http://hybrid-piloten.shirtinator.net/',
'target' => '_blank',
'show' => true,
),
),
),
'stromtankstellen' => array(
'title' => 'Stromtankstellen',
'href' => 'http://elektro-piloten.de/map.html',
'target' => '_blank',
'show' => true,
),
),
),
elseif ($context['current_action'] == 'moderate' && $context['allow_admin'])
$current_action = 'admin';
if ($context['current_action'] == 'start')
$current_action = 'start';
Also I changed the filename of the two new files from home.php and home.css to start.php and start.css so it is the same as my action name.
But: a click on the community titled button leads not to my start page but to the forum index. It seems something is missing which tells ElkArte which URL it has to open when clicking on the start page button (called "community" for those of you who will test it here).