Improve UX & performance of drag-and-drop in the Events editor > Expression editor
When dragging an element from the canvas or from the outline, it is quite often unclear whether the user has successfully "picked up" an item to drag into the expression editor. Sometimes, the mouse pointer ("cursor") changes from an open hand () to a grabbing hand (), sometimes not.
When dragging, the user needs to have some sort of "object" in "hand" so that they feel that they're actually dragging something: a simple rectangle with a dotted or dashed outline will do, ideally positioned according to relative location of the mouse pointer on the object they intend to drag.
Also, when the expression editor is topmost, performance drops dramatically. Justinmind becomes very laggy, dropping to 2 or 3 frames per second, even on a relatively high-end MacBook Pro (2.6GHz Intel Core i7 with 16 GB of RAM).