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 using a vertical tool slider:
Width—controls the width of the line using a vertical slider next to the tool's location. Slide up or down to set the width.
The following settings can be adjusted from the context toolbar:
Keep selected—when enabled (default), the new shape layer will be selected on creation. When disabled, the new object is deselected which prevents it from adopting the next object’s stroke/fill properties.
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.
Convert to Curves—converts the selected object into a series of connected lines and nodes.