I cannot see an option to upload a file or any option to download a specfic file using the Desktop app. I have installed the app for Android and can both upload and download files.
The menu in the top right gives the options to Disconnect and Set Password.
Right-clicking on a folder gives the options to create a New Folder or Paste.
The menu for a file has the following options: Cut, Copy, Copy Link, Delete, Rename, Email and Open.
The version of the Desktop app is 126.96.36.199
The firmware on the EX2 is 1.05.25