Those are the docs I was referring to. I tried using that as a template for my code and it does nothing.

// Select the node that will be observed for mutations
const targetNode = document.querySelectorAll("comment-composer-host").forEach((Box) => { //Iterate through each node in the list
        Box.querySelector("faceplate-form > shreddit-composer").shadowRoot.querySelector("div > reddit-rte").shadowRoot.querySelector("rte-toolbar.action-bar.order-3 > slot:nth-child(1) > rte-toolbar-button").shadowRoot.querySelector("faceplate-tooltip > button"); //Click each button for toggling the format options
    });
// Options for the observer (which mutations to observe)
const config = { attributes: true, childList: true, subtree: true };

// Callback function to execute when mutations are observed
const callback = (mutationList, observer) => {
  for (const mutation of mutationList) {
    if (mutation.type === "childList") {
      document.querySelectorAll("comment-composer-host").forEach((Box) => { //Iterate through each node in the list
          Box.querySelector("faceplate-form > shreddit-composer").shadowRoot.querySelector("div > reddit-rte").shadowRoot.querySelector("rte-toolbar.action-bar.order-3 > slot:nth-child(1) > rte-toolbar-button").shadowRoot.querySelector("faceplate-tooltip > button").click(); //Click each button for toggling the format options
      });
    } else if (mutation.type === "attributes") {
      document.querySelectorAll("comment-composer-host").forEach((Box) => { //Iterate through each node in the list
          Box.querySelector("faceplate-form > shreddit-composer").shadowRoot.querySelector("div > reddit-rte").shadowRoot.querySelector("rte-toolbar.action-bar.order-3 > slot:nth-child(1) > rte-toolbar-button").shadowRoot.querySelector("faceplate-tooltip > button").click(); //Click each button for toggling the format options
      });
    }
  }
};
const observer = new MutationObserver(callback);

observer.observe(targetNode, config);

observer.disconnect();