it is not currently possible to tell from the saved filters list which filters are global (and which are shared by group)
the preset filters that exist today the project overview as well as the home portal are very similar to global filters, but they are static – we can't change them.
we'd like to see the concepts of preset filters and global filters merged. if a shared filter had search criteria specific to a given project, it would appear only on that project's list. otherwise it would appear on all projects lists, as well as the saved filters list (so it could be run cross-project) with an icon delineating that it was shared.