Firstly, you need your own theme. In this theme, create the file classes/core_renderer.php
Add:
include_once($CFG->dirroot . "/blocks/navigation/renderer.php");
class theme_THEMENAME_block_navigation_renderer extends block_navigation_renderer {
protected function navigation_node($items, $attrs = array(), $expansionlimit = null, array $options = array(), $depth = 1)
{
if (is_array($items) && count($items) > 0) {
$items[0]->children->remove('1', 20);
}
return parent::navigation_node(
$items,
$attrs,
$expansionlimit,
$options,
$depth);
}
}
(Note the 20 in ->remove('1', 20) is required. I think this is a bug and you should be able to pass null here - this is discussed at https://tracker.moodle.org/browse/MDL-53383 )
Do post with any improvements! Thanks