There are a couple of commands that can be used to manipulate the slider. I haven't had time to try out each command, so let me know if they work for you. You can execute the command under a context menu (maybe the map context menu) or as an I Want to button.
Context Menu: Site > Viewer > Context Menus > Map Context Menu
I Want To Menu: Site > Viewer > I Want To Menu.
Try the toggle command first: ToggleTimeSliderActions
If that doesn't work, try two separate buttons: HideTimeSlider / ActivateTimeSlider
Let me know how it goes.
The ToggleTimeSliderActions command only changes the sub options for the slider. Does the same as clicking the arrow. HideTimeSlider will hide the window, and ActivateTimeSlider will show it again. Looks like there needs to be a click for on, and click for off.
This works though, but can I make the Time Slider control hidden by default?