Function set_enabled_in 

pub fn set_enabled_in(
    target_dir: &Path,
    eco: &Ecosystem,
    game: &str,
    full_name: &str,
    enabled: bool,
) -> Result<()>

Enables or disables an installed mod in target_dir: applies the on-disk file toggle through the install layer, then flips enabled in mods.yml. Errors if the mod is not present in target_dir.

A mod-loader pack (see Ecosystem::modloader_package) is a no-op here, matching r2modman: loaders can’t be disabled, so neither the on-disk files nor its enabled flag are touched.