Sub-Widget "Add" Button

Inside of a section widget, you have your selection of sub-widgets as I call them.
However, you can only manipulate the available sub-widgets and if you accidentally closed too many and you need an additional sub-widget, you must completely remove the entire section widget and start over.

It would be most useful if there were a "blank" option when adding a section and also an "add" button to add sub-widget windows