Missing group selector for searching criterias 'Reporter' and 'Assignee'

It is nearly impossible for a user (e.g. the project-leader) to search items being reported by all members of a group or beeing assigned to users of a special group. Why: Like for users the search fields doesn't display a selector windows for groups! Hence, that standard users aren't aware of the group names and in fact it is hard to remember how all the groups are named it is for our JIRA-users impossible to use this very important search-criteria.