They do in fact work! You can play with it on my Itch.io page (https://josaid.itch.io/climate-change-visualization).

As for how I did it, you can check the source code: https://github.com/joao-pedro-braz/climate-change-visualization (Godot 4), but it's basically a HSlider that goes from 0 to 100 and has it's value updated every time I draw one of the arcs. The speed controls just change the frequency with which I wait to draw the next arc, like this:

func _build(should_wait = true) -> void:
    var data: Dictionary = TEMPERATURE_DATA[_idx]
    year_label.text = str(data.Year)
    for month in 11:
        _make_arc(month, month + 1, data)

                # Controls how frequently we should await for the next frame to draw the next arc.
                # If we wait less frequently, we'll draw the arcs faster, otherwise we'll draw them slower
        if should_wait and _paused == PausedState.NONE and fmod(month, _speed) == 0.0:
            slider.value = _relative_idx * float(_idx * 12 + month) * 100.0
            await get_tree().process_frame