This module is part of Tuleap Entreprise. It might not be available on your installation of Tuleap.
This widget is still under development
You may want perform a search based on several trackers and several projects. A widget “Cross tracker search” enables you to do that.
For now it allows you to search by bunch of 30 “Open” artifacts. If you use the query, the retrieved artifacts will match the query and not only the “Open” ones. The query uses the TQL language. You can find more information about the query format here.