If that money sits there in U.S. dollars or any other central-bank issued paper money then "sitting" money is a non-issue. Central bank can increase money suppl

If that money sits there in U.S. dollars or any other central-bank issued paper money then "sitting" money is a non-issue. Central bank can increase money supply and direct it through government or banking system to holes digging efforts to keep current employment levels (aka monetary easing). The hard part is to unwind it when that money which was sitting there starts moving. Then we will probably see some inflation. Easing is easy, tightening hard.