How to make Windows 11 fill my Mac screen when not using an external monitor

My 2023 14-inch MacBook Pro runs Windows 11 with Parallels. I use my Mac with a 27-inch external monitor most of the time. If I disconnect from the external monitor, MacOS looks normal—the desktop adjusts to the dimensions of my laptop. If I switch to Windows, the screen looks just like my wide-screen monitor, only smaller. How do I make Win11 VM desktop display in full screen when not connected to an external monitor?