I see this is an older post, but as I am finishing up a regulator replacement and ran into this green shim piece falling loose as I pulled the passenger window, I will make some notes.
As noted, the green shim goes on the forward part of the window, closer to the body. It sits behind the regulator tab, but in front of the rubber grip with the female threads that the bolt tightens down to hold the window.
This is when sitting inside the door, looking at the panel side.
The shim is angled, so shifting it up widens the gap, and pulling it down shrinks the gap. The outer grooves sit on the matching nubs on the back side of the regulator tab, then the rubber grip piece sits behind it.
lined up the shim so the bolt fits the slot on the green shim before tightening down on the rubber grip pieces female threads. Fairly certain the tab on the green shim should face towards the interior door panel side,
my pictures show it both ways as I was adjusting it to check. The images should help clarify any confusion with my previous statements.