In this YouTube video at this point in time the designer makes the node segment smaller symmetrically so that it stays centered by using the keyboard, but it does not show the shortcuts.
How is this done?
I learn something new nearly every day:
How To Make a Trapezoid in Inkscape
Draw a rectangle.
Convert it to a path (Path > Object to Path)
Use the node select tool (F2) to select the two corners of the rectangle that you want to adjust to form a trapezoid (You have to hold down the shift key to select multiple nodes).
Press the comma or period keys to move apart or bring together the nodes.