Yeah, it hasn't been working for a bit. It doesn't come up in search, but here's the thread: Smartly inject not working in 2.3.3
You can replace a bit of code and it will allow you to drag and drop again. When you click save it will copy the new JSON to your clipboard where you can then paste it manually over your current dashboard JSON. It's not ideal, but it restores the drag and drop and resize functions.