ed by either an input or an output. When an output references the control&#8217;s id, executing the control updates that output. When an input references the controld&#8217;s id (via the &#8220;action_id&#8221;), updating the input executes the control. The two control <cite>type</cite> options are &#8220;button&#8221; and &#8220;hidden&#8221;. &#8220;button&#8221; will add a button to the left panel. No control is added to the left-panel for control_types &#8220;hidden&#8221; (this is useful for linking a 