Recently I decided to sort my landmarks. I never did that ever since I joined SL in 2006, so you can imagine how huge and messy my Landmarks folder was! Now it's all pretty and arranged in folders but still there are landmarks in various clothes or furniture folders, and it's hard to notice the repeating ones. I could have of course checked folder by folder, or have randomly typed names of stores or places, but I wanted something easier and faster. And I found the way! When you open the map, you can use the drop-down Landmarks list to spot groups of similar landmarks. These are all landmarks from your inventory sorted alphabetically, so it's really easy to find the ones you can delete. You still have to go to your inventory to sort them out, but at least you know what you're looking for.