Since the automatic skin download feature has been introduced there's less need for a skin manager. If you want to search for a skin you've seen used by someone when racing online, just view the skins_x folder with a program like IrfanView.
Being able to view and download all the skins that are uploaded to LFSW would waste bandwidth, since you're going to automatically get the skins you need whenever you go racing online
BTW, I delete all the skins inside skins_x folder every once in a while to save disk space, since I'm always gonna get the skins people use when I go racing