Allows items to be snapped to drag slots on specific items, most notably the building blocks. Feel free to suggest items that would benefit greatly from drag slots, preferably with a diagram or a sketch.
Features
Aligning dragged item to hovered slot
Customizable snapping radius
Optimize management of slotting actors
Orienting dragged item using the drag slots as the placement origin
Not actually related to item snapping, but it has been a pet peeve of mine that you were restricted to 15° rotation increments when rotating items with the scroll wheel. Decided to expose this to the player while I was implementing drag slots.
That is actually a feature that is probably not explained anywhere (and I discovered it just now as well). Holding the alt key changes the rotation increment to 1°, which I think is still pretty useful for quick and dirty-yet-precise rotation with the scroll wheel.