With the release of HelpDesk 3 - Version 3.5.5 you can now set a category ID within the FAQ and Support embed code.
The embed code has received a new var called catID.
w.lcjUrl = u; w.catID = '';
Now you can set any of your category ID into the embed code and it will load the category instead of the main view.
w.lcjUrl = u; w.catID = '1';
It will load the FAQ with the Category ID 1 or preselect the support area with the deparment ID 1.