a45,
или так
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<input id="taskEdt" type="text">
<hr>
<ul id="todoList">
<li><input type="checkbox">Задача 1</li>
<li><input type="checkbox">Задача 2</li>
</ul>
<script>
const taskNameEdit = document.getElementById("taskEdt")
const todoList = document.getElementById("todoList")
taskNameEdit.onkeydown = e => {
if (e.key=="Enter" || e.keyCode==13){
let chEl = document.createElement("input")
chEl.type = "checkbox"
let taskLiElem = document.createElement("li")
let txt = document.createTextNode(taskNameEdit.value)
taskLiElem.append(chEl, txt)
todoList.append(taskLiElem)
taskNameEdit.value = ""
}
}
</script>
</body>
</html>