Recently I found my estimated 100 desktop symbols re-ordered in 5 bunches: 4 bunches with one in each corner and one bunch in the middle (leaving more space for more crowd between the bunches :). Unfortunately I was not aware how my symbols have been arranged in that way, I cannot find any menu entry nor do I remember the short cut that I might have pressed accidentally. Do you know how to invoke this function? Since I tried out some Apple menu items I found, I now ended up with the desktop arranged by the grid. But I prefer the bunches.
Update: Ops, it happened again. I hardly assume this automatic arranging of my desktop happens when I connect an external display in mirror mode having a smaller resolution. Now it looks as follows:

Notice the stacking of symbols in the top right that is the result of a formerly "Clean up" command in the desktop's context menu. But anyway, Mac OS created these 5 bunches again. As there is obviously a feature like that implemented, I am curious if I can run it also manually without connecting an external display to make it happen.