The Trapezoid Tool has options on the shape and on the context toolbar to change the position of the top corners. This sets the length of the top edge (base) and the angles of the lateral sides (legs).
Settings
The following settings can be adjusted from the context toolbar:
Left/Right Point—controls the position of the top-left/right corner of the trapezoid from left (0%) to right (100%), with 50% representing a central point.
Mirror—updates the above settings to give a reversed (flipped) version of the current shape.
Negate—updates the above settings to give the inverse (opposite) of the current shape.
To Curves—converts the selected object into a series of connected lines and nodes.