Delete the Play button when launching a storyline in Rise

This is my workaround for this. 
I create a duplicate of that first slide and insert it into Storyline as my new first slide. If there is audio, I will remove it. If there is video, I will create a screen capture and replace the video with the jpg. I just created. I'll then change the timeline of my new slide to 0.25 sec and create a trigger to jump to the next slide when the timeline is complete.  By doing this, you no longer have audio or video on your first slide and from the end-user perceptive, your new first slide passes in a blink and the audio/video will begin how you originally wanted it to.