Compute the index of the current task list item using only other task list items.

src/task-lists-element.ts

@@ -132,7 +132,11 @@ function position(checkbox: HTMLInputElement): [number, number] {
   const list = taskList(checkbox)
   if (!list) throw new Error('.contains-task-list not found')
   const item = checkbox.closest('.task-list-item')
-  const index = item ? Array.from(list.children).indexOf(item) : -1
+  const index = item
+    ? Array.from(list.children)
+        .filter(el => el.classList.contains('task-list-item'))
+        .indexOf(item)
+    : -1
   return [listIndex(list), index]
 }