To monitor a set of critical variables, you can mark them for the Watch list. The Watch list shows the absolute path to the variable and the value. You can also enter a new variable value in the Watch list. The Watch list shows only variables that you access by using an absolute target path, such as _global or _root.
If you add a local variable to the Watch list, its value appears only when Flash Player stops at a line of ActionScript that is within the variable’s scope. All other variables appear while the SWF file is playing. If the Debugger can’t find the value of the variable, the value is listed as undefined.

Add variables to the Watch list
Remove variables from the Watch
list