custom-element,
import-element {
  display: none;
}

is-visible,
is-hidden,
repeat-list {
  display: contents;
}

/* Only while REALM is starting or importing definitions, so tags it never defines stay visible. */
:root:has(custom-element, import-element:not(:defined), import-element:state(loading))
:not(:defined) {
  visibility: hidden;
}