So I had a go and managed to do what I wanted to do. I created a button and then assigned an action to it so that when the button is clicked it triggers this script:
var vid = document.getElementById("video");
vid.currentTime = 3;
It works and when the button is clicked it takes me to the specified time in the video and plays the video as well. However, when the video playback comes to an end, clicking the button only takes me to the specified time but doesn't play the video. Is there anything I can do to make it play the video as well.