Custom Nodes

The "group elements by type"-feature in the treeview is a nice feature.

Would it be possible to create a feature that allows the placement of own nodes and group elements by users choice? Let say, the default treeview shows all types of elements, tables, functions, procedures and so on. If I now could create own (grouping)nodes, for example a node "anything01" and could move some procedures, functions, triggers and so on (drag & drop) as childs...