Simply an application that can help you to quickly build other applications. A GUI Builder with code generation capabilities for Python Tkinter. Collaborations are highly welcome :)
Widgets placed on the Design Window cannot be destroyed if a mistake is made. The solution which seems unreasonable is having to close the who GUI one is working on and start all over again. You make a mistake, you start over; this should be fixed.
The widget tree window that contains a list of every widget created on the design window can solve this. It should have a feature that allows you right click on a widget listed and delete it - and probably perform some other options.