title: Modify a Google Slides presentation while presenting?
body: <p>I'm afraid I already know the answer, but maybe someone else has found a way to do this.</p>
  <p>I've been perusing the Slide Apps Script reference, and I'm excited about the possibilities. One thing I would like to do is alter a slide mid-presentation. Specifically, I would like to somehow indicate a link has been clicked.</p>
  <p>If links in a presentation turned purple like web links I would settle for that, but I would like to use a trigger when a certain link is clicked or when a certain slide is shown. This trigger could run a script that alters the slide with the link appropriately to show the link has been clicked or even remove the link altogether.</p>
  <p>I know the Slides API is behind the others, but Forms have installable triggers that can run <code>onFormSubmit</code> and Spreadsheets have triggers that run <code>onChange</code> and <code>onEdit</code>. I would love to see Slides have an onPresent trigger that ran a script that could detect slide changes with methods like <code>onSlideChange</code> that could report currentSlide. That way we could run scripts while the presentation is showing and take action based on current slides or links.</p>
  <p>Aside from Slide specific triggers being added to the API, is there any way to modify slides during a presentation? Or at least show that a link has been clicked?</p>