The control section of PaperUI will show only those channels of things that are linked to an item.
Note that PaperUI is not meant to be used as the UI for daily useage, only for administrative tasks!
“PaperUI is meant for administrative tasks” does not mean to remove it.
You are currently faced with an administrative task - adding Items and linking them to channels of your Things.
This is the job PaperUI is meant for, setting up your system.
When it is set up you will probably use another UI that you can customize for your daily needs. And use PaperUI only occasionally.