If people haven't known of the Member Grouper of Visual Studio yet, here is a simple screenshot for the main UI for ideas:
As can be seen, it has various options supporting different functionalities. It can group class/type members per class basis, document basis, project basis, solution basis, or selected projects. In addition, the member grouping rules can be edited with some nice and easy to use UIs and different rule can apply to different target. The member grouping rules can be saved into a central folder so that next time when the Member Grouper starts up, the same grouping rules will be populated into the session automatically.
Only when the Some Projects option is chosen will the Apply/Project/Rule data grid be enabled so that different grouping rule can be specified and applied to a different project if wanted.