My solution to challenge

/* Select the elements we'll need, namely the paragraph, text input, and button, and assign them to const variables. */
const toggleList = document.getElementById("toggleList");
const listDiv = document.querySelector(".list");
const Descriptioninput = document.querySelector("input.description");
const DescriptionP = document.querySelector("p.description");
const DescriptionButton = document.querySelector(".list button");
const listUl = listDiv.querySelector("ul"); //find the ul within the div
const addItemInput = document.querySelector("input.addItemInput");
const addItemButton = document.querySelector("button.addItemButton");
const list = listUl.children;

const addVisibility = (list) =>  {
    let firstListItem = list.firstElementChild;
    let lastListItem = list.lastElementChild;
    let allUp = list.querySelectorAll( ".up" );
    let allDown = list.querySelectorAll( ".down" );

    for( let i = 0; i < allUp.length; i++ ){
        allUp[i].style.visibility = "visible"; 
    }

    for( let i = 0; i < allDown.length; i++ ){
        allDown[i].style.visibility = "visible"; 
    }


    let topUp = firstListItem.querySelector(".up");
    topUp.className = "blocked";
   // topUp.style.visibility = "hidden";

    let botDown  = lastListItem.querySelector(".down");
    botDown.className = "blocked";

};

const attachListItemButtons = ( li ) => {
    let up = document.createElement("button");
    up.className = "up";
    up.textContent = "Up";
    li.appendChild(up);

    let down = document.createElement("button");
    down.className = "down";
    down.textContent = "Down";
    li.appendChild(down);

    let remove = document.createElement("button");
    remove.className = "remove";
    remove.textContent = "Remove";
    li.appendChild(remove);
};

 const setButtons = (list, listUl) => {
    for (let i = 0; i < list.length; i++) {
        attachListItemButtons(list[i]);
    }

    addVisibility(listUl);
};

//these two handlers are attached to the containing div but need to access the element triggering the event to make the changes to that element
listUl.addEventListener("click", (event) => {
    if (event.target.tagName === "BUTTON") {
        if (event.target.className === "remove") {
            //get target target list
            let li = event.target.parentNode; //the button is the event so its parent is li
            //get target list parent node
            let ul = li.parentNode; // the li parent is ul
            //remove child
            ul.removeChild(li);
        }//end remove

        if (event.target.className === "up") {
            //get target target list
            let li = event.target.parentNode; //the button is the event so its parent is li
            //need prev sibling as a reference
            let prevLi = li.previousElementSibling;
            //get target list parent node
            let ul = li.parentNode; // the li parent is ul
            if (prevLi) {
                //insert
                ul.insertBefore(li, prevLi);
            }
        }//end up button check

        if (event.target.className === "down") {
            //get target target list
            let li = event.target.parentNode; //the button is the event so its parent is li
            //need prev sibling as a reference
            let prevLi = li.previousElementSibling;
            let nextLi = li.nextElementSibling;
            //get target list parent node
            let ul = li.parentNode; // the li parent is ul
            if (nextLi) {
                //insert
                ul.insertBefore(nextLi, li);
            }
        }//end down button check

    }//end check for button
    let li = event.target.parentNode;
    let sendUl = li.parentNode;
    addVisibility(sendUl);   
});

toggleList.addEventListener("click", () => {
    //If button was clicked then we hide it. If clicked again unhide
    if (listDiv.style.display === "none") {
        toggleList.textContent = "Hide List";
        listDiv.style.display = "block";
    } else {
        listDiv.style.display = "none";
        toggleList.textContent = "Show List";
    }

});

//add event listener to listen to when button is clicked
DescriptionButton.addEventListener("click", () => {
    DescriptionP.innerHTML = Descriptioninput.value + ":";
    Descriptioninput.value = "";
});

//we need to create 3 buttons and append to list item
addItemButton.addEventListener("click", () => {
    //return collection which is sim to array
    let ul = document.getElementsByTagName("ul")[0];
    let li = document.createElement("li");
    li.textContent = addItemInput.value;
    attachListItemButtons(li);
    ul.appendChild(li);
    addItemInput.value = "";
    //add to dom
    let sendUl = li.parentNode;
    addVisibility(sendUl);
});

setButtons(list, listUl);