
I am thinking and started something with forms at IDE for this propose:
To make a generator source to help making or for preparation for the NEW InputWindow() and I draw-up these shootscreen for your appreciation:
I hope you enjoy to know my expected utility. But do not need to make any comments...

In the first picture (at grid, first column). I will put all defined keys into ComboBox. It will be more easy for the final user.
The adjust controls item, will try to display the InputWindow and I will add some Spinners just to adjust widths sizes (as Marek made in one post).
I think is going to help for better understanding of NEW InputWindow and it usage.
Even our IDE is missing many elemental resources, I love to use IDE for forms designer.

Rgds