I'm trying to place a hidden video on my page, triggered by a seperate play button to play full screen. There isn't an option to display a poster image, so I'm not sure how to go about hiding it. Any ideas?
In the Media panel, choose None for Poster. That will make your video object invisible. Then scale the video object down and add a non-interactive play button on top of the video object so that users can tap it to play the full-screen video. (You can also create a separate button with a Video > Play action.)