@Ed Ockelton > It may be helpful that after you use "Bridge" or import new tracks into your Rekordbox Collection, make sure you right click on the Column Title bar, and make sure there is a √ beside "Date Created". NOT "Date Added" because it will be different.
Once you have √ Date Created, select it in the Column Title bar and your tracks will sort from the most recently added to first added. If it's in reverse, just click it again and it will change the order. Them you can search through all your tracks you have added in the last XX amount of days and then send them over to a new playlist.
Let me know if that helps any.