Dragging references from one module into the other is way faster than publishing the producer and adding the reference using the Manage Dependencies. It's also much safer, because you can consume the reference before it's even published, so you reduce the impact of your change to other developers.
But dropping the reference into the consumer module has a catch. There are just a small number of pixels on the screen that you are allowed to drop a reference on. These are the eSpace node (the root of the eSpace tree), some folders depending on the object you are dragging, and a few others. All of these drop zones are inside the eSpace tree, and there's a high probability that all of them are hidden behind the scroll. In this scenario, you would have to slowly and carefully scroll until the nearest drop zone, or cancel the drag and start over - which is faster.
There's also the problem of hovering the tab of the consumer, and then moving the mouse to the eSpace tree without mistakenly hovering another tab in the way.
A quick win would be to automatically scroll to the top of the eSpace tree when dragging an object from another module. This way, at least one drop zone will be visible: the eSpace node.
A better approach would be to have a large drop zone that appears when dragging, and it could cover most of the Service Studio window, just like gmail and google drive.