Performance - Preload Images

jwb-bizvergence

• In order to improvee LCP on a site that uses a query loop slider as the large hero on the home page, PageSpeed Insights suggests that "fetchpriority=high should be applied" to the primary image for the page.
• My research on the forum suggests using the Performance - Preload Images area located in Theme Settings to apply this HTML to the url of the image.
• However when I attempted to do this, the box simply emptied itself when I clicked the Save Changes button.
• What could cause the disappearance of the code in the box?
• And, second, is there an alternate, better way to accomplish the application of the fetch priority?