Function radio_group_keys 

pub fn radio_group_keys(
    commands: Commands<'_, '_>,
    keys: MessageReader<'_, '_, KeyPressed>,
    tracker: ResMut<'_, FocusTracker>,
    store: ResMut<'_, PropertyStore>,
    radios: Query<'_, '_, (Entity, &RadioButton)>,
    disableds: Query<'_, '_, (), With<Disabled>>,
    orders: Query<'_, '_, &DocumentOrder>,
)

Arrow keys while a radio holds focus: move selection to the next / previous enabled group member, WRAPPING at the ends (web radiogroup; unlike tabs, which clamp). Selection follows focus - the newly focused member is selected immediately (Qt/GTK). Also moves the Focused + FocusVisible markers and the tracker.