in scripts/navigation-loader.js [185:195]
function handleTocButtonClick(event, navId) {
const tocPart = document.getElementById(navId);
if (!tocPart) {
return;
}
tocPart.classList.toggle(TOC_PART_HIDDEN_CLASS);
const isExpandedTOCPart = !tocPart.classList.contains(TOC_PART_HIDDEN_CLASS);
const button = tocPart.querySelector('button');
button?.setAttribute("aria-expanded", `${isExpandedTOCPart}`);
safeSessionStorage.setItem(`${TOC_STATE_KEY_PREFIX}${navId}`, `${isExpandedTOCPart}`);
}