/* Widen only the submission page’s main column */
body.pkp_page_submission .app__page.width--narrow {
  max-width: max-width:70rem;   /* try 1100–1200px */
}

/* Optional: keep it comfy on small screens */
@media (max-width: 768px) {
  body.pkp_page_submission .app__page.width--narrow {
    padding-left: 16px;
    padding-right: 16px;
  }
}