If you process all of your RMA items at a central location, you can bulk-edit their location by using Inventory Detail.
Filter your search results to "Inventory Process: RMA Process." (You may also have to filter for "All Time," if the items were initially added outside of 90 days.)
On the Inventory Detail page, you can batch edit their location by selecting multiple items and clicking "Edit Selected." You can select the Location attribute, choose the transfer location, and note the transfer.