1- create several items in sequence with -1.00 fades (ex: claps, where steep fades are used to cut to silence)
2- lasso select a bunch of them and ctrl-drag them to the right
3- allow them to overlap as you drag, but don't release mousebutton
4- BUG: fade type is reset after REAPER attempts to crossfade them while being dragged.
reproduced on a portable install as well