How to keep prefab item dragging

on the OnMouseDown event, a prefab object would be instantiated in the current position of the mouse.
When the mouse button is still Down, I’d like to drag that object, until the mouse button return up without having the second click to drag it again.

Try parenting the new prefab object to the mouse world position when you instantiate it. Though I believe you’d have to update the position every frame using the Camera’s ScreenToWorldPoint() function to keep it dragging, and unparent it when the user lifts their mouse button.