no-stacked-banner.css

/* initially hide all banners except the first one */
.notice-banner {
  display: none;
}

/* show the first banner that is not dismissed */
.notice-banner:not([data-dismissed='true']):first-of-type {
  display: flex;
}

/* show the next banner when the current one is dismissed */
.notice-banner[data-dismissed='true'] + .notice-banner:not([data-dismissed='true']) {
  display: flex;
}

.notice-banner {
  position: absolute;
  top: 0;
}