Lists are the ReadCube Papers equivalent of Folders. 

You create a list by clicking the gear symbol next to All Papers

Screenshot showing where to create a List in ReadCube Papers app

And then you can just drag and drop papers into that folder!

To create a nested list (folder-within-a-folder), select the folder you'd like to move into another list on the dialogue box:

Screenshot showing how to organize Lists and add a sub List

Or, you can also drag a list inside another list.

To create more layers of organization, we recommend using Tags