Archive group forums to node: This option can found in group options (http://domain.com/admin.php?options/groups/tl_groups/). An forum which all group forums will have this node as parent. If this option have been omitted or invalid node, the group forum won't not have parent node. Whenever this option change the value, the group forums also update their parent node. Suggestion: The archive forum node should not display in list (meaning: do not check the option Display in List while editing this node) then all group forums will not display in your forum index. I high recommend to set this display order of this node to higher as possible, it's make this node always to bottom and all group forums bottom as well.