Remove custom widgets from Page Builder area in Big Commerce

I've been experimenting with creating custom widgets but I'm not sure how I remove custom widgets in the Page Builder area in Big Commerce? I've successfully deleted the widget and deleted the placement via the APIs and cannot see them (via the APIs) but I still see them in the Page Builder (even when clearing the browser cache), i.e.

Ok further reading has led me to understand that the custom widgets in the page builder (as I referred to them in the question) are actually custom widget templates. So deleting them is as the API