Элемент добавлен, но не отображается в nextElementSibling

var currentClosable;
var currentContent;
function selectedColl() {
    document.getElementById("inputTaskDiv").style.display = "block";
    currentClosable = event.target;
    currentContent = currentClosable.nextElementSibling;
    var inputTaskDiv = document.getElementById("inputTaskDiv");
    currentContent.append(inputTaskDiv);
}

var taskCounter = 0;
function addTask() {
    var text = document.getElementById("taskInput").value;
    // create a new div element and give it a unique id
    var newTask = $("<input type='checkbox'><label>" + text + "</label><br>");
    newTask.id = 'temp' + taskCounter;
    taskCounter++
    // and give it some content
    var newContent = document.createTextNode(text);

    $(currentContent).append(newTask); //Why isn't it being displayed??
    console.info("appended");
}

var elementCounter = 0;
var elementCounterContent = 0;
var text;
function addElement() {
    text = document.getElementById("input").value;
    // create a new div element and give it a unique id

    var newDiv = $("<button class='collapsible' onclick='selectedColl()'></button>").text(text);
    var newContentOfDiv = $("<div class='content'></div>");


    newDiv.id = 'temp' + elementCounter;
    newContentOfDiv.id = 'content' + elementCounterContent;

    newDiv.classList = "div";
    elementCounter++
    elementCounterContent++
    // and give it some content
    var newContent = document.createTextNode(text);

    // add the newly created element and its content into the DOM

    document.getElementById("input").value = " ";
    $("body").append(newDiv, newContentOfDiv);

    newDiv.click(function () {
        this.classList.toggle("active");
        content = this.nextElementSibling;
        if (content.style.display === 'block') {
            content.style.display = 'none';
        } else {
            content.style.display = 'block';
        }
    });
}

.collapsible {
    background-color: #777;
    color: white;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 15px;
}

.active,
.collapsible:hover {
    background-color: #555;
}

.collapsible:after {
    content: '\002B';
    color: white;
    font-weight: bold;
    float: right;
    margin-left: 5px;
}

.active:after {
    content: "\2212";
}

.content {
    padding: 0 18px;
    /* max-height: 0; */
    /* overflow: hidden; */
    transition: max-height 0.2s ease-out;
    background-color: #f1f1f1;
}

<script src = "https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<input id = "input" type = "text"><button onclick = "addElement()">Add</button>

<div id = "inputTaskDiv" style = "display:none">
    <input id = "taskInput" type = "text"><button onclick = "addTask()">Add Task</button>
</div>