This appears to be a great example of a multi-cloud integrator (MCI). A term which I - ahem - just made up. But the idea is clear, all your online accounts are integrated - to a degree. So you can search across online 'drives', view content and generally copy things around. This is the UWP version for all Windows 10 devices, including phones.

From the Store description:

Woopiti is a free universal file manager that allows you to access all your files no matter where they are, and perform countless actions such as upload, download, copy, move, delete, share, send by email, SMS or Bluetooth, among others. And if you forgot where your files are, don't worry, Woopiti has a search engine that searches across all your accounts.

Supports: Facebook, Dropbox, Google Drive, OneDrive, Youtube, Google Photos, Flickr, Twitter, Instagram, Box, Mega.co.nz, SugarSync, CloudMe, HiDrive, 4Shared, OwnCloud and WebDav.

Some screenshots to illustrate the app in action, this time under Windows 10 on the desktop (though it also works fine under Mobile):

The full range of online services that are supported - with some set-up wotk within Woopiti, you can shuffle content around to stay within space limits, if needed.

Browsing content, here in Box...

Woopiti UWP is in the Store here. It's free with IAPs to remove some limitations.