floppies_dir
The option documentation is properly formatted yet
Default: [base_dir]/Floppies
Search for (relative) floppy image paths relative to this dir (in addition to current directory).
This means that if you have a floppy image "Test.adf" in the Floppies directory, you can for example simply set [floppy_drive_0] = Test.adf (without including the directory path).
Source: https://github.com/FrodeSolheim/fs-uae/blob/master/docs/options/floppies_dir