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Атрибут Icon Type CSS Class в вашей версии имеется ? Значение в Icon Type CSS Class соответствует классу коллекции иконок ? fa в данном случае.

Icon Type CSS Class
A CSS class used to specify the type of icons used for all nodes. This class is used in CSS rules to specify properties for all icons of that type. The icon type along with the value of the icon column of the region source determines the icon CSS classes used for each node.

Typical values are:

a-Icon This allows using a small number of built-in APEX icons such as icon-circle or icon-tree-folder.
fa This allows using Font APEX or Font Awesome icons. The Universal Theme makes one of these icon libraries available.

If no value is given there is no icon type. The icon type CSS class, if needed, can be included in the icon column. For example the icon column value could be "fa fa-user". For a tree with no icons set the Icon Type, and Default Icon attributes to empty and in the SQL Query source the icon column should be null. Custom or third party themes may have their own font or CSS sprite icon library and use a different icon type/prefix class that you can specify here.