This looks great. I currently use Sortable.js via Vuedraggable but I was never a big fan: https://sortablejs.github.io/Sortable/

I came across Shopify's recently which has an amazing website: https://shopify.github.io/draggable/

In Firefox I noticed some flickering when dragging a lower item to the top edge of the black box on this page: https://www.dflex.dev/demo/lists/asymmetric/ it might need some debouncing or something since it appears to be repeatedly redordering when it's in right on the edge/border (might not be a standard usecase but it was noticeable).