Function drain_timer_commands 

pub fn drain_timer_commands(
    events: MessageReader<'_, '_, ScriptCommandEvent>,
    timers: ResMut<'_, TimerRegistry>,
    wake: Option<Res<'_, WakeDeadline>>,
)

Read SetTimer / CancelTimer commands emitted by the script’s builtins this tick and update the TimerRegistry accordingly, then ask the loop to wake at the earliest pending deadline. Without that request an idle loop parks on events alone and a timer armed from a click fires only when some unrelated input ticks the app.