content.js

const sidebarInitObserver = new MutationObserver((mutationsList, observer) => {
  const targetElement = document.querySelector(".notion-sidebar");
  if (targetElement) {
    observer.disconnect();
    const expandedObserver = new MutationObserver(expandedObserverCallback);
    expandedObserver.observe(targetElement, {
      subtree: true,
      childList: true,
      attributes: false,
    });
  }
});

let previousExpanded = null;

function expandedObserverCallback(mutationsList, observer) {
  const targetElement = document.querySelector(".notion-sidebar");
  const sidebarData = JSON.parse(
    localStorage.getItem("LRU:KeyValueStore2:sidebar")
  );
  const expanded = sidebarData["value"]["expanded"];
  if (expanded !== previousExpanded) {
    targetElement.style.display = expanded ? "block" : "none";
  }
}

sidebarInitObserver.observe(document.body, { subtree: true, childList: true });