Function fit_flag 

pub fn fit_flag(
    registry: &dyn ParamRegistry,
    field: &str,
    key: &str,
    on: bool,
    reason: &str,
    confidence: Level,
) -> Mapped

A switch set on or off.

A key outside the registry, a legacy key or a key that is not a switch gives no edit and a not_in_synth entry.