Favorite filters in Preside listings are awesome and I can't live without them. But the more they are used, the more cluttered the UI gets. Here comes the solution:
It would be great to have custom groups of favourite filters. If a fav filter is in a group, then the group is displayed, hiding the fav filters. those related fav filters are visible in form of a drop down menu beneath.
Fav filter groups are display first in list. All fav filters not in a group are displayed afterwards, as done now.
Fav filter groups may be personal, global or shared, much in the same manner as fav filters. The should be freely editable.