Can we not just have something like:

  a {
    &:hover {…}

    &:parent(.theme):hover {…}
  }

No crazy selectors with an ampersand in the middle allowed, but a way to apply a parent or ancestor selector, a bit like :where() or :is(). There could be :in() for ancestors.

No one needs this monstrosity:

  dialog {
    @nest html:has(&[open]) {…}
  }