Has

Note that ordering matters in the above selector. Swapping the nesting of the two pseudo-classes would result matching any element which contains anything that’s not a heading element.

section:has(:not(h1, h2, h3, h4, h5, h6))

5 or more children

Make a list of 5 or more children a flat list.

ul:has(:nth-child(n+5)) li {
  display: inline;
}

Adds semi-colon after each item in a list excepts last one

Add a separator except to the last one.

ul:has(:nth-child(n+5)) li:not(:last-child)::after {
  content: ';';
}

where:

nth-child and last-child are child selector