EDIT: This appears to be due to a Firefox bug that will be fixed in the next major Firefox release. In the meantime, you can open the full-tab view and Drag and Drop will work there.

Thanks, I'm happy to hear you like it! I promise I didn't remove the drag-and-drop ability; if it's not working for you, would you mind opening an issue on GitHub and sharing a screen recording of what's going on? I'd be happy to look into it, it's certainly possible that some of the styling changes might've caused a problem I missed in my own testing.