Select an individual girder. All girder cross sections will be displayed automatically.
Single-click a blue slice to select it. The selected slice will turn orange. Section Attributes will appear in the Stack for the selected girder.
Right-click and choose Add Cross Section or Duplicate Cross Section.
Use the orange slice to choose a location for the new cross section. Click again to place it.
Attributes for the selected cross-section will display in the Stack.