fullscreen
The option documentation is properly formatted yet
Description: "Start emulator in fullscreen mode" Default: 0 Example: 1 Type: boolean
Open the emulator in fullscreen or windowed mode (1 = fullscreen, 0 = window). The default is windowed mode at 960x540.
Source: https://github.com/FrodeSolheim/fs-uae/blob/master/docs/options/fullscreen