When you call a function that is traced, LispWorks collects information about the arguments it was called with and the values that it returned. This information is printed to the trace output stream, which might be the Listener or the Background Output. In addition, if a Tracer tool is on the screen, the information is shown in its Output Text view and collected in its Output Data view in a tree format.
Each call is a node in the tree with a 
icon. Double-click on it to show the source of that function, if available, in the Editor.
A call node has several kinds of subnode:
icon shows the arguments passed to the function. Double-click on it to show the arguments in the Inspector. Expanding this node shows each argument with its name (if known) as a subnode with a yellow 
icon. Double-clicking on one of the arguments shows that argument in the Inspector.
icon shows the value or values returned from the function. Double-click on it to show the values in the Inspector. Expanding this node shows each value as a subnode with a 
icon. Double-clicking on one of the values shows that value in the Inspector.
represent folded data. These are older calls which are hidden automatically to reduce clutter. Expand this node to reveal the folder data.
icon represents an uncaught throw (control transfer) along with the catch tag. Expanding this node shows each thrown value as a subnode with a 
icon.
You can collapse the tree by clicking on the 
toolbar button.
You can clear the trace output data from the display by clicking on the 
toolbar button.
You can restore the last cleared output data by clicking on the 
toolbar button.
LispWorks IDE User Guide (Windows version) - 13 Sep 2017
icon show calls to traced functions within the parent function.