stack items dense on ground

I have seen it a few times. People throw stuff to trade on the Ground (in this case many keys).
And they are stacked very densly on the Ground. And they blink at the same time.
Is this something one can do intentionally?
It's great, you can pick up stuff much faster and I would like to do it

Yeah, when you press lobby there is an option there called item spacing that can be checked/unchecked.

Wait. Have I been playing wrong? Is everyone unchecking the item spacing button? I never knew what it did, so have always left it checked, assuming it was a random QoL introduced in d2r.

That change was introduced mostly for controller play I believe. Speading things out is a bad thing normally IMO. In fact, I think in some cases it may even be detrimental - spreading out drops over a larger area and onto non-droppable locations resulting in missing drops. I mean, stuff still sometimes drop onto a location where stuff can't drop (for example, there are some places in

The Forgotten Tower where drops vanish if you kill a ghost on top of it), but no point in making it worse

omg that is so much better for Ground-trading many items. THANK YOU !!

remaining question is: why do they blink at the same time? I was not able to reproduce regardless how fast I drop

Got it: when someone already has dropped the items and THEN you join, they blink in sync

In many games, if you drop items rapidly in the same spot, they can stack on top of each other. Try dropping the keys (or other items) in quick succession without moving, so they fall in the same location.