To be able to create own groupings for subcontractors it is possible to work with tags. That way it is possible to select these groups through several filters.
There are no limits to what type of tags that can be used, as these are created by respective users. The selection in tags only shows the tags that have already been posted. Read more about filter settings here.
Add a tag for the Subcontractor view by the + - button.
Sort out desired subcontractors in the list of subcontractors by using the Tags filter.
By clicking on a tag you get an overview of all areas where the tag exist.