Data transfer from marginnote 3 to 4

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With the recent update, i have tried to transfer data to marginnote 4.
All my documents and study set have been transfered. My issues are multiple.

  1. After transfering, i deleted all my documents and study sets from marginnote 3, still it is taking 20gb storage on my iPad which is double the size of my MarginNote4 app.

So, if there is nothing in my marginnote 3 then why is it taking all this space? Or have the files not been transferred correctly?
Also, all the files synced are part of which app on iCloud. If i delete the marginnote 3 sync on iCloud, will my MarginNote4 files and study sets disappear?

  1. There is no option to sync the documents to iCloud . I am confused between local folder and cloud folder. The unsynced files in local folder have no option to sync it to iCloud.

Kindly help, I am completely reliant on MarginNotes. All my study notes are in it, if the files are lost, my year long work would vanish

Thank you.