additionalLines

Key	Type	Default Value
additionalLines	Map<String, String>	mapOf()

The additionalLines setting is a map of additional lines that you can add to the options.txt file. This setting is useful for adding custom settings that are not supported by Stonecraft.

build.gradle.kts

modSettings {
    clientOptions {
        additionalLines = mapOf(
            "fullscreen" to "true",
            "bobView" to "false",
            "pauseOnLostFocus" to "false",
            "modelPart_cape:true" to "false"
        )
    }
}

Stonecraft does not do any validation on the values you provide in the additionalLines setting. It is up to you to ensure that the values are correct and that they are supported by the game.

You can find the list of all valid options on the Minecraft Wiki