It would be really great in wikidata for there to be a "create new item" link in the dropdown menu for when you want to add an item to a property, but the item does not exist. The current workflow is to try to add an item, see it doesn't exist yet, navigate away from the page, and then create a new item, navigate back to the original page, and then add it.
(Even better would be if it were possible to create an item without leaving the page, i.e. create an item by name and then directly add it from the page, maybe in a pop-up. Then, presumably the user could go on to expand the newly created item.
The tool could even be extended to add citoid support for references by allowing users to add items as references this way, and attempt to use citoid to fill in some of the parameters. (T131661).
This project could start life as an on wiki Gadget and then later be added to the WikibaseRepository extension. )