Deleting some previous flight plans from drop down box


Been using Flightaware for six years and in that time have accumulated a huge list of previous flight plans that appear in the “populate using previous flight plan” dropdown box on the flight plan filing page. I use about a half dozen of them all the time and the rest I may never fly again. It would be nice if I could cull the losers from the winners. The way it is now the plans I use all the time are mixed into this huge list making them inconvenient to find. Anybody know how to delete some of this list? Thanks.