After the little bug with the temp folder appearing in the content browser was appearently fixed in 4.8p4, it still shows up.
If you add a new level from the “levels” tab/window, a save dialog opens. The save dialog shows the temp content folder.
If you click on cancel, from then on, the temp folder will also be visible in the regular CB tree.
After the editor is closed and reopened, the temp folder is hidden again.