Option in Balances -> view as list
Like the view as chart page... the view as list page can have a drop down list box... which lets you display only open transaction and hide all the other persons. Right now, the view as list displays all my friends including the ones that I have settled up with. There can be an option which says "list only open transaction members"

Update: We added filters to the mobile apps to do this and we also hide friends/groups you have been settled up with for at least 30 days in most places.
We are currently in the process of redoing how our friendships and groups are presented to our users. I think being able to parse this information and hide the friends/groups that don’t have any balance is a great idea.