To create a lander folder you need to click Landers > Lander Folders in the sidebar.

Then proceed to click New Lander Folder button, give it a name and choose users who have access to it.

Then you would be able to move all your existing landers to a new folder in bulk. Go back to Landers > Landers List, choose landers you want to put in a folder in bulk by ticking them off and click "Move to folder" and choose the folder you want to move in.