Most dialogs in GCP remember their last size and location. If you use a dual screen monitor and move the dialogs to the 2nd display, they will appear there when launched.
If you then run GCP on a single display, the dialogs may display off-screen. Simple to fix and a great tip for all Windows software.
Tip 1: Typed key combo: (Window Key) +Shift+→ to move the dialog on screen. You may have to use the ← key depending on what side the 2nd display is positioned.
Tip 2: Most GCP dialogs will re-center if the shift key is held down when issuing the command.