By default the debugger tool appears as shown in Debugger tool below.
The debugger tool has two areas, and a toolbar. These are described below. If you invoke the debugger tool by clicking Debug or Debug Snapshot in a notifier window, the tool also contains a listener pane. This provides you with a useful way of evaluating Common Lisp forms interactively in the context of the error.
This area displays the error condition which caused entry to the debugger. You cannot edit the text in this box.
The error condition can be operated on by commands in the Condition menu. See Performing operations on the error condition for details.
The backtrace area displays the function calls on the execution stack. Each tree root or list item in the backtrace area represents a stack frame associated with a function call.
Double-clicking on any stack frame finds and displays the source code definition for that function in the Editor, if this is known. Any frame selected in this area can be operated on using the commands in the Frame menu, which is also available as the context menu. See Performing operations on stack frames for details.
The backtrace is displayed either in a tree or a list, with the behaviors described below.
You can choose which type of display it uses by the Frames and Arguments preference, described in Configuring the debugger tool.
When the Frames and Arguments preference has the value Tree-view , the Debugger appears as shown in Variables in the Debugger tree view below.
Each expandable root node in the Backtrace: tree represents a stack frame associated with a function call. You can operate on the frame as described in Backtrace area.
Expanding a stack frame node displays any variables associated with that function call. You can double click on any variable to inspect it using the Inspector tool. Any items selected in this area can be operated on using the commands in the Variables menu: see Performing operations on frame variables for details.
Figure 11.2 Variables in the Debugger tree view
Each call frame is a root in the tree with a 
icon and has several kinds of subnode:
icon represents a closure variable (either from an outer scope or used by an inner scope).
Double-click on a 
icon to show the source of that function, if available, in the Editor. Double-click on any of the disc icons to show that variable in the Inspector.
When the Frames and Arguments preference has the value Two list-panels , the Debugger appears as shown in below.
Figure 11.3 Debugger tool with two list-panels
Each item in the Backtrace: list represents a stack frame associated with a function call. You can operate on the frame as described in Backtrace area.
A second list titled Local variables: shows the local variables of the frame which is selected in the Backtrace: list. You can operate on the variables similarly to the backtrace tree - double click on a variable to inspect it or use the commands in the Variables menu, which is also available as the context menu.
Note: with Two list-panels , only the local variables of the current frame are displayed.
At the top of the debugger tool is a row of buttons, as described below. Click:
If you hold the mouse cursor stationary over any button for about one second, then help text appears that identifies the button.
If you prefer a Debugger tool to appear immediately, without the intermediate Notifier window, set *enter-debugger-directly* to a true value.
LispWorks IDE User Guide (Macintosh version) - 13 Sep 2017
icon represents a normal lexical variable. 
icon represents a special variable.
icon represents some other frame.
to break the current execution.
to return from the debugger and invoke the continue restart.
to return from the debugger and invoke the abort restart.
to select the previous stack frame in the backtrace area.
to select the next stack frame in the backtrace area.
to print the backtrace in the Listener.
to print the variable bindings of the current frame in the Listener.
to find the source code for the current stack frame.