When I work with UI, it would be very convenient to use drag and drop from Project Window. Right now when you drag a sprite from Project into the Scene View, even if you drag it inside Canvas Unity, create a Sprite object instead of an Image.
Maybe there is some way to write a custom handler for object creation in a Scene View when you drag it from Project?
not that i myself am aware of no, i have always right clicked on my object i want to place my new UI element on within a canvas and click image. it makes a small white square and in the inspector i drag my sprite into source image. then set preserve aspect if it requires and then move and resize as needed. still sort of a drag and drop solution but not in way ur thinking.