Lists are the ReadCube equivalent of Folders.
You create a list by clicking the plus symbol at the bottom of your left hand menu:
And then you can just drag and drop papers into that folder!
To create a nested list (folder-within-a-folder), you can click the gear icon beside the folder you'd like to move into another list, and nest it in another list:
Or, you can also drag a list inside another list:
To create more layers of organization, we recommend using Tags