I get a lot of friend requests, and I use a combination of categories and nicknames to help gauge who stays and who goes. In short, if they belong in a category, they stay on my friends list. Everyone in the default "Friends" section gets removed after several weeks if I don't interact with them. However, with the new Steam friends UI, I can't seem to find any way to get the default "Friends" category back.
How can I see all my Steam friends that don't belong to a category?