Most of PaperShip user have less than 10 folders.
So unfortunately we didn't develop feature to collapse folders.
PaperShip 3.2 is now available: https://itunes.apple.com/app/papership-for-mendeley-zotero/id631980748?mt=8
We added the collapse collection feature in it: just swipe to the left a folder and you'll be able to collapse/expand it.
We hope you will really do appreciate the effort we put in it and you will promote the app to your colleagues as well.
Also, don't forget to give us feedback.
You should be able to swipe (swiping to the left) on folders, and see a “Collapse/Expand” button. Of course, this button is only available for folders actually containing subfolders.
The last version of PaperShip should now save the state of the collapsed/expanded folders.
As usual, if you enjoy this feature, please add a review on the AppStore as it helps us a lot: https://itunes.apple.com/app/papership-for-mendeley-zotero/id631980748?mt=8
We're working on this feature. Any beta-tester would be appreciated ;)