Project broker: disabled for assessment tool, assessable child elements not visible

The project broker is treated as an non-assessable element, but "produces" assessable data. In order to be able to assess this data, authors can employ the assessment course element.
Elements can be grouped together either by grouping them under the structure element, or by adding related elements (such as the assessment element would be to a project broker element) as childs.

Whereas the assessment element is visible in the assessment tool when e.g. being a child to a wiki element, the assessment element is not listed when grouped under a project broker.