/* Newlines (\a) and spaces (\20) before each parameter */
dt i.sig-param:not(dt i.sig-param:only-of-type)::before {
    content: "\a\20\20\20\20";
    white-space: pre;
}

/* Newline after the last parameter (so the closing bracket is on a new line) */
dt i.sig-param:last-of-type:not(dt i.sig-param:only-of-type)::after {
    content: "\a";
    white-space: pre;
}