You can achieve this by patching WayFinder this way :
1) in the definition of the snippet (into the modx admin interface) add this at the right place:
’hideLevel’ => isset($hideLevel) ? $hideLevel: 2,
2) in the call of the snippet, you must use
&hideSubMenus=`true` &level=`0` &hideLevel=3
3) you must also patch the WayFinder class : for version 2.0, replace the line 65 by
if (!$this->_config[’hideSubMenus’] || $this->isHere($parentId) || $level < $this->_config[’hideLevel’]) {
That’s it

I would like to propose this patch for the next version of WayFinder, how to do it ?