I wrote a similar app for archivists to push materials into preservation repositories. I used Electron, since it has good cross-platform support. The source is at https://github.com/aptrust/dart with documentation at https://aptrust.github.io/dart-docs/users/getting_started/

The underlying JavaScript code in that app started getting messy because I was working on several other projects simultaneously, but you might find it useful to play with as you consider your desktop app.

The archival community uses a simple text-based packaging format from the Library of Congress called BagIt, which allows you to include metadata and checksums with your archived materials so you can ensure their integrity and make sense of them when you get them back.

Anyway, you're working on an interesting problem. I'd be interested to see how it goes.