A number of operations can be performed on functions selected in the Text area (when in the text view) or in the Callees or Callers areas, or on the current function (when there are no functions selected elsewhere).
The Function menu gives you access to the standard actions described in Performing operations on selected objects.
The Function > Trace submenu gives you the ability to trace and untrace the functions selected in the Text, Callers or Callees area.