There have been quite a few threads on the new bookmarks. My response on this (in the Bookmarks ease-of-use thread) was:
You cannot currently transfer bookmarked recipes to a different bookmark. The easiest way to do it currently is to filter by your custom bookmark, choose the minimized data View as option (the left icon) then click the chefs hat down each one selecting I Want to Cook This or I've Cooked This. Don't bother deleting your custom bookmarks as you will be deleting those at the end. Once you have done all your recipes, go to Bookmarks under your My Bookshelf tab and delete your custom bookmarks. To check out how long it took I just did 112 of my recipes that I had tagged as Do Later and it took 6 minutes. I did find there were quite a few I had tagged that I am no longer interested in!