As with other tools, you can configure the way package names are displayed in the debugger tool in the Package box of the Debugger Preferences.
Check Show Package Names to turn the display of package names in the Backtrace and Variables lists on and off.
Specify a package name in the text box to change the process package of the debugger tool. You can use
completion
to reduce typing: click on 
to which allows you to select from a list of all package names which begin with the partial input you have entered. See Completion for detailed instructions.
By default, the current package is the same as the package from which the error was generated.