The dictionary window for any installed scripting additions can be opened directly in Script Debugger.
Choose File > Open Dictionary. In the resulting hierarchical menu, you’ll see a list headed AppleScript. Choose Scripting Additions.
In any open dictionary window, locate Scripting Additions under the AppleScript heading in the dictionaries list at the left. Click it.
In the dictionaries inspector, locate Scripting Additions under the AppleScript heading. Double-click it, or select it and click Dictionary, or select it and choose Open “Scripting Additions” Dictionary from the contextual menu.