Refactor my VueJs script and remove the library

Hi and glad your are viewing this project!

This is a rather simple project were I need you to refactor a current Vue3 script. The thing is that the current library that is in use doesn't allow users to drop "items" into other items, only rearranging and moving items in the list.

So what I need is to keep the original functionality and be able to sort items in the list/array. With the added functionality that "items" can be added to other items. In my example I will use "questions" can be moved into "topics".

All other functionality that vuedraggable and Sortable.js offers seems to be bloat at this time.

I prefer that the application is built with the "HTML Drag and Drop API". https://developer.mozilla.org/en-US/docs/Web/API/HTML_Drag_and_Drop_API

I have an example application here at stackblitz:
https://stackblitz.com/edit/vue-hssmu8?file=src/App.vue

And here is an example of the problem from one of my developers screens:
https://www.youtube.com/watch?v=YMs5cJP5o_g

So "topics" in subjects can be rearranged.
"Questions" can be rearranged
"Questions" can be inserted/moved into "topics" array.