It's in the "config.plist" file of your OpenCore directory. Edit this "config.plist" file with an appropriate tool like ProperTree (
https://github.com/corpnewt/ProperTree ).
As an advice I would recommend when you're modifying/experimenting with OpenCore config:
1. to get a backup of your EFI folder on another medium
2. to get a replica of your good/working EFI folder onto a bootable USB drive (just in case your mess with something on your boot drive config), just to ensure your can still access your MacOS installation by booting your computer from that USB drive
3. even more careful advice: make a replica of your EFI folder onto a second USB drive and make your experiments with OpenCore config directly on that drive.