I use an histogram widget along with usual widgets. As soon as I add some (not all) checkbox widget there are problems with filtered results Eg : unfiltered results : the aggregates show 2 matching results for a value I click the aggregate widget ...
Usually, Nuxeo Studio exposes widgets that deal indifferently with users or groups. In the case of aggregates such as selectManyListboxUserAggregate, it seems this is not the case. Unfortunately, some fields in custom documents do hold a reference ...