I don’t see a way to modify the embedded Figma prototype link once added to Slides. I am looking in the toolbar when selecting this Embed object but don’t see settings. It would be nice if there was a URL field to paste in a diff one and work more quickly (maybe it auto refreshes then) or a button.
Check out how Maze dot co (app) is integrated with Figma links and you have more tools to edit your prototype settings right within Maze.